One of the biggest reasons back filling sucks (IMO) if youre actually going to try and make an honest effort when you join-
Is the sheer ult economy situation you often walk into.
Very rarely does someone lose a literal single team fight, go “Screw this”, and then leave. Often theyll feel like theyre bashing their heads against a wall, give up- and ditch. Enter you to to fill their position.
Problem is when a game is that far in already- Youre often walking into a game where a lot of people are already well on their way to having their ults, or outright have them. And lets be real, youre often joining into the losing team, so youre often walking into a situation where the enemy has a bunch of ults, and you / the team youre on- dont.
Youll then spend the next few team fights getting farmed by enemies who have ults, while inefficiently building your own.
Not 100% certain what if anything could/should be done to fix this. Immediate obvious idea is having some kind of boost to building ult charge- maybe have it based on the duration the game has been going on (So if you join a game 3 minutes in, youll get a longer boost than joining a game thats only been running for 45 seconds), and only work until your first ultimate has been gained?
Has this been / does this feel like an “issue” for anyone else?