This is just a proposal for what an MMR formula should consist of and not just be which team won.
This would obviously be a lot of work and maintenance that riot wouldn't want to go through but if they did then we would have a much better system.
Firstly these things should be taken into account
1. Win or loss. This still needs to be a major factor in MMR no matter what
2. Kill participation. People always say "objectives win games" but having a number advantage helps secure those objectives
3. Warding. Riot would need to add something which prevents people spamming wards in base but warding is a major part of LoL
4. Objective control. Things like taking dragon, taking turrets are all important and having good objective control is paramount
5. Champion and role diversity. If you only play Kat mid and troll whenever you don't get mid then you are not as good as someone who has mastery of all roles
6. CS. This would be very minor but if someone consistently has 300+ cs they deserve to be recognized
All of these would be dependent on what role you are playing which, as we can see from the frequently played champion, is able to be recognized and so when you play support you are not expected to have a lot of CS but have more wards, and when you play top you are expected to have lower kill participation but more CS.
Secondly this should affect your LP
1. People who DC, AFK in base or something along those lines should take a percentage of everyone else's LP loss
2. Length of game. If you manage to delay the game to 50 minutes you deserve to lose less LP than a team that surrenders at 20
3. Vice Versa for point 1 as if you win a game which was a 4v5 most of the way then you deserve more credit
All of these points would not be major but would just be something to help differentiate people more than just win/loss
Is there anything I missed?
tl;dr if you don't want to read it don't read it and don't comment