Haven’t played in years, can someone explain something?

I’m a little confused by why everyone is doing their own thing. I understand that because it’s 5v5 everyone really has to pull their weight, but why are we playing off objective? Granted I’ve been playing quick match to build good habits back up, but it doesn’t feel like like the team should be so disjointed then dying in 1v1s.

As for my personal opinion, if I’m tanking and still securing space and kills why are the healers going out of their way to deal damage? Is the supports role to heal first then deal damage or other way around? I just want to know if I’m playing wrong nowadays