It doesn’t take hours for me to form a party and the reason i do it is not because i want to avoid toxicity. I don’t really care about toxic players and i’ve won games with toxic players and even bots in my team.
The point is that this is a team game and getting new random teammates doesn’t really make sense if someone wants to play this game a bit more seriously. Improving as a team and becoming more efficient/coordinated is what makes this game fun for me. Maybe leaving this game was the best decision for you since a “team focused” game doesn’t seem to suit your interest.
Maybe not saying a word was wrong. You could wrote down some counter arguments and why this guy deserves a report and maybe he would not be able to convince others to report you like that. Anyway it’s only 3 reports (if they really did it and not just said it) so what? If this happens every game to you then it might really be the case that your drafting upsets a lot of players…
Strategically it makes sense to let many options open for the last pick and not force him to fill some mandatory roles. You can play QM if you want to play a specific hero.