What are the most played to least played classes in order as well as most complex to least complex classes

It's difficult to answer your question in its entirety, since you're asking for a numerical ranking.

The least complicated class is probably Cra. Iops, Ecas, Enis are also easy to play. Osas are solid, as are Pandas.

You cannot really say that there is one particular most complicated class, as the feeling of difficulty of a certain class is always subjective as you may learn certain mechanics easier than others.
However, the difficulty rating by stars of certain classes certainly bears some truth to it. A Cra is easier to play than say, a Masqueraider or a Feca, while a Xelor or Eliotrope will be harder to play than either of those three. I can't speak from experience for the Rogue or Sadida however, not having tried them.
Personally, however, I believe that the mechanics for the Xelor and Eliotrope are somewhat bordering on just being a hindrance which reduces the enjoyability, if this is even a word, of those classes. I have not been able to really get the hang of how to make Telefrag work effectively for Xelor on anything more than a single or two enemies at a time yet, and for the Eliotrope, while I have a decent grip on how the portal mechanics are meant to work they often just turn out as a hindrance for placing them and casting spells through them because the exit point is always specified to be one exact portal depending on the entry point and its position to the portals inbetween if you have more than two, and often the turns do not last long enough to be able to plan around that or adjust accordingly. I may not be the best Eliotrope player in existence but I know it well enough to usually make it work, however if we actually could choose where a portal or spell comes out of another portal without having to always place ourselves in the opposite way to the placement of where the enemy is or where we want the portal to appear, like it is in Wakfu, it would be much better in my opinion(and correspond more to the fact that with them being copies of an Eliatrope, they should be portal masters and be able to choose how and where the spell comes out of any portal, instead of having to place themselves around it opposite to the enemy or spot that is intended to be hit). I'd even be willing to sacrifice the bonus damage for launching a spell through a portal for that.

Personally, I can agree with the post made by Diablo saying that the classes he mentions as easy to play are that. They should not be complicated to handle/learn, at least a Cra is not. I personally like Sacrier quite a bit too, and I think it's also fairly easy to play. The only real thing to pay attention to is when it is better to use negative or positive suffering depending on the circumstances, which is something that you should learn soon enough, or at the very least once you get to Level 100+.

Cras are probably the easiest to play, you just try to stay at a distance while you pick the enemies off or build your hard hitting attacks. Iops are a bit like that but more melee/close combat oriented.

then what might you say the most popular classes are? would it be reasonable to assume that the easier ones are the most popular amongst new players, but the 2 and 3 star ones are more popular amongst veterans who mostly worry about dungeon runs and pvp, consequently they need more advanced mechanics to achieve their goals?

The main reason i asked about numerical rankings was because I recall when i was playing like 6 years ago, cra were horrifically powerful for minimal skill paired with weapon proficiency with daggers made them very popular in pvp and kolo. While xelor were considered very useful in pvp and dungeons because they were among the best at ap raping bosses and large mobs.

would it instead be easier to rank the difficulty of the hardest classes within their own star ranking? eg the *cough cough* CONVOLUTED 3 stars (xelor, elio, sadi, rogue). I care the most about them because...well most of my higher level characters fall in the three and two star range...and looking at the conditions to make X thing happen if Y thing isnt also happening, but R happens if your grandpa's birthday is in less than two months excluding the possibility of him being born on a leap year... Thats really what the harder classes conditions read like to me. ofc i know relearning the class is inevitable, but based on prior experiences with this game if later i find out that "oh yea, rogues are ok. but like feca do literally the same thing with far less headache and are actually much better at it," im going to strangle someone.

It isn't possible for me to bring up any particular numbers when it comes to how many people play certain classes as to my knowledge, there is no reliable way for anyone not directly affiliated with Ankama to see how many people play a certain class, and those numbers vary depending on servers too, I'd say.
But one thing to keep in mind is that most players likely would not play the classes rated at a three star difficulty, so I don't think numbers would really be a reliable indicator in every case. And considering the results you *can* get with a Cra for not much effort, it wouldn't surprise me if it is a very popular class amidst most of the playerbase. I have one myself but don't particularly find its playstyle very engaging, even though I have a tendency to prefer ranged combat over close/melee combat. I only started to play a few months ago however, so I can only rely on older forum posts to compare Cra in its current status to what it used to be when I say that it probably isn't quite as powerful as it used to be but it can still put out some pretty decent damage, given what I have seen players do with it, so long as they were aware of what they were doing and/or didn't screw up or get screwed over by something out of their influence.

Regardless, I would assume that, most likely, the one or two star classes definitely are more popular amidst players as they are easier to play/master but can also get fairly good results out of them. The best thing I could suggest if you wanted to find out some numbers is to check your individual characters on your profile(if they still exist) but those only show your position in the various shown populations without really telling you what their total number is.

Currently, based on forum posts I've seen here and there, Xelor's AP reap/steal doesn't seem like it particularly stands out compared to other classes, right now. And it does not seem like it is particularly useful in late game PvM due to monsters' high AP steal resistance and/or high number of AP. Don't know for PvP as I do not play it and generally have a rather limited interest in it.

As for rating the three star classes in their own way... I do not think I can really do that since I lack experience for both Rogue and Sadida. Even if I did, it would be subjective as I would likely have a harder or easier time learning their mechanics than someone else. But I can't deny the results that can be gotten out of these classes if they are played properly.
Either way, I personally find Xelor harder to get a grip with than an Eliotrope, partially because I can't really get my head around how to get Telefrag on multiple opponents reliably. I played it up to Level 80 and haven't gone further with it so far.

Also, every class is unique in its own way, or at least most of them have some sort of unique aspect even if some others may seem similar(like I mentioned above, Xelors' AP reaping not standing out in any particular way right now, compared to other classes, given the posts I've read myself, or to name another example I recall being mentioned in posts, the shield mechanic not being a particularly unique feature of the Masqueraider since other classes can also shield themselves with the spell variations). A Feca certainly won't be doing what a Rogue does(a Feca has glyphs but cannot use bombs or create bomb walls using them, nor use the bombs themselves to inflict damage or buff themselves). Nor is there a class which can create portals and has the associated bonuses of launching its spells through them(except for the damage bonus) like the Eliotropes(which, in all fairness, are just Eliatrope knockoffs in a way, given how they were created by accident - you might have guessed by my profile picture that I like Yugo, an Eliatrope, quite a bit, and my Eliotrope is my favorite character in Dofus... it's just not the highest leveled as I had started playing on my Sacrier first and was impatient to progress the story - I like to play with portals quite a bit and to use them to prevent taking damage from enemies as much as possible). There are some similarities here and there but I do not think the classes really resemble each other too much.

This site has some statistics

https://statofus.com/en/classes

I like Sram very much