I don't think most people have a huge problem with the pre-role selection. That's a feature some people wanted for a while and is a nice merger between teambuilder and old draft pick.
That said, there are still some shortcomings to it. There's no benefit to playing more than 2 roles well. There's no option to queue for more than 2 roles but not all 5 (what if I want anything BUT X). There's people who only play 1 or 2 champions in a role they enjoy, but can't comfortably queue for that role, especially when those champs are strong (which is when they would want to play it most!) (because when they're strong they're more likely to be pick/ban leaving you without options). Queue times are necessarily longer (as someone who'd be willing to play support 10% or 20% of the time is now never playing it, etc...) (people who played support secondary up to 50% of the time are going to get sick of being assigned it every game and will choose a different secondary).
Overall though, I think the benefits of role pre-selection (never being stuck in your worst role [especially during your promos], never having an ally stuck in a bad role and feeding, overall more fun in-game because you're playing something you enjoy, arguably more competitive because of the first points) probably outweight the costs.
The problem with dynamic queue is the whole premade groups thing. I, and I'm sure a lot of other players, am getting really tired of how much Riot is pushing social play. Not to mention that their metrics are probably off on it anyways!
All of these bonus IP weekends that reward you for queuing as a group: I used to get double IP solo before on those weekends and now I can't get anything solo and need to find a group. So obviously I join chat rooms to find groups and then the groups have terrible chemistry because no one cares how good people are and you get diamonds queuing with level 17s and the games are terribly imbalanced and those weekends become even more on an IP grind. Now there are these hextech rewards that are better for people who queue as a group.
Then let's ignore the free rewards, because they are well, free, and we should just be grateful to Riot for getting anything. Dynamic queue (i.e. grouping premades) hurts ranked play a lot. Ranking loses credibility under this system (you can get carried by your 4 allies pretty easily). Getting grouped with a premade is often less fun (you're blamed for their mistakes because they won't blame eachother, if they include the jungler you're never going to be ganked for even when you need it or it's the best move, etc...). You're left out of communication in some cases (if they're on voice they won't type or ping). I'm not saying ALL premades are bad, in fact I've been queued with premades and done so well with them (and because of them) that they've invited me to queue with them for the next game (and I wish I could do more but I rarely have time to play more than 2 games in a row - but that's my problem). There's a bunch of benefits to premades (most notably you can't complain about being unable to climb due to bad luck as you can now choose all of your allies if you truly believe that's your case) but in this part I feel the costs outweigh the benefits.
I think the large majority of players are solo players, and they're feeling more and more screwed.
