Can’t right-click people to avoid anymore?
I believe the default keybind is “P” on PC (or maybe it’s “O”, try both). Either way, there’s a list of players you recently played with. It’ll show their icon, their user name, and the last hero they played. From there you should be able to right click them and select “Avoid as teammate”. Just like OW1 it only lasts 7 days (you can remove it if you want though) and you can only have 3 people on said list. You should be able to do it after a match too.