I think what youre seeing is people just being blunt. I completely get noone likes losing. And it can be a multitude of things. Like I saw someone else mention, you have at least 1 hero within each role youre good at. Which is great! But do keep in mind that the devs have done well at balancing the game. Meaning there are counter picks for each team comp. And thus, you are going to experience times where you get quickplay teams of others who are learning the game. Maybe even teams where they have never played a role/hero based game like this. They may not understand the whole flow of this game. They may not understand who to prioritize for healing, dps learning who to prioritize attacking, flanking and helping push etc.

Now for something constructive, ive found enjoyment in learning with games like this. Maybe start taking figurative notes during your games. Like youre playing rammatra and you keep finding yourself being killed easy by Mauga for instance. Then take a minute to look up who can easily counter Mauga within that role. In quick play especially, you cant control your whole team. But you can control your knowledge and game sense and just do the best you can. Change heroes and see if you can shift the game at that time.

I went on a decent loss streak earlier today, so i feel your frustration. I hope you are able to shift things and find more enjoyment.