Unless you play the majority of your games in off peak hours, it should be very rare for you to face full 5 man teams. You didn’t say in your post if you were speaking of QM or SL, though you mentioned climbing, so I guess ranked?
The short answer to your question for both modes is, group up with friends. This was the way the game was intended to be played, the lack of useful LFG features like clans would suggest otherwise.
Again, yes being with friends help. If this is QM and you’re playing solo it’s often better to play with a very self sufficient hero, rather than a more niche hero like Genji. Sonya is a safer pick as an example, she has good macro, decent damage, can double soak lanes, grab merc camps fast, has good self sustain, has counters but none that will render her useless.
Do a search on these forums about “abusive chat” punishments and you will see it works for that. You might notice there is a pinned AFK topic about punishments. It’s out of date, but I’ve received an occasional email about someone I’ve reported for AFK.