If your assists are meaningful: you did decent damage, gave useful stats, landed cc on the enemy, ok.
If you got 12 assists because you accidentally landed some aoe/had an aura and you happened to walk nearby by mistake, well, we have a problem there.
Also the KDA count treats kills and assists the same way: it's (kills+assists)/ deaths
If you are positive, or even better with a kda of 3 (doing good) or of 6 (carrying hard) nobody will complain except fuckers that are just looking for an excuse to flame you.
If you are 0/4/12 just keep not throwing, farm it up and keep working towards victory and nobody should have the right to tell you anything.
Be the attention whore yasuo that jumps 1v85924 just to show off how good he is at pressing E, and your score will suffer.
Also kindred is shit right now, let's make our voice heard by riot to have them fixed since right now it's probably one of the bottom 5 worst junglers.