it has some issues to be perfected like you said... you selected two roles got another role that someone else selected and they got your role. stuff like this dont need to happen but i think its a complicated issue with trying to make even matched games via mmr etc and what have you...
if you put a higher mmr player on a team but put him in a autofill/off role it might make up for the difference of mmr that person has over the other team and so on ( i dont know this for fact just a theory )
so its an issue of match making plus making queue times as fast as possible and not all players having equal skill in multiple of roles
back in the day before they dynamic queue , role selection and auto fill we had draft pick and we all honored "pick order" ( most of us ) and usually the 1st pick got their choice of role/champ and had control of all bans... 2nd pick got to choice of what was left and so on... til you get down to last picks on each team those players were forced to fill roles...
people did it , didnt like it... said it cost them games getting force to fill roles they didnt play or so on... however every one ( high elo/streamers via guides ) said you need to know how to play at least 2 champs in each role ( outside of your main ) to play rank effectively now with the new system you see more 1 tricks, people who legit dont play anything BUT TOP or whatever role and has zero to little clue how to play multiple champs/roles
people are more "specialized " in their skills instead of general skill and knowledge of game /roles
so then when you get filled into roles you dont play or have someone on team who is it creates a power imbalance in the match making where people make the claim the team with the less autofills win ( which is theory is true, but why) well cuz of people one tricking and being specialized in only certain roles/champs
so while auto fill seems bad... and it might cost some games and pissy players. in the end its better for game by allowing /forcing if you may... players into more roles. learning more, playing more roles/champs matches ups and just more general knowledge
in time i think it will plateau and it wont be as much of a deciding factor
( just my thoughts)