One of the best pieces of advice when playing:

It's important to remember you have little to no control over what other players do in the game. You do however have control on what you yourself choose to do

We often spend far to much time and effort obsessing over what our teammates are supposed to be doing (and worse playing as if they are), when the odds are they are going to keep on not doing it. Instead what you should be thinking of is what can you do yourself to change the situation.

If your teammate won't group up then going in 4v5, no matter the fact that he should have been with you, doesn't make it any less suicidal. If he keeps overextending, no matter how much you yell at him odds are he will keep overextending.

However if you know what they are going to do, no matter how bad it is, then you can find ways to compensate or even take advantage of what they are doing wrong. Follow the guy who won't group, or split. Use the guy who extends as bait and counter-gank. Someones not warding their lane? Ward for them, it might be stupid that you need to, but as noted: you can't change that player but you can take actions yourself to bring victory in sight.

Heck one game the adc didn't know what dodging was and kept getting pulled by blitz grabs, the natural reaction is to watch her suicide and then get angry at her for being so bad. Instead I elected to throw myself into blitz grabs, despite being nearly as suicidal for myself, however with our main dps staying alive we were able to come around and win the match, instead of being a 4v5 with no damage.