Has quick play felt rough since the new hero arrived?

If one hero is taking over your attention, try treating a few matches as practice against that hero rather than expecting every game to feel even. Notice what situations make them effective, then adjust your positioning or swap when it makes sense. That may not fix a rough match, but it gives you something useful to focus on besides whether your team counters them.

Honestly, you don’t have to keep playing the mode that’s wearing you down. Try a different mode for a while, or set a small limit for quick play and call it when the matches stop being fun. A break is a perfectly reasonable option too. No need to force yourself through a whole season just because you recently came back.

There are two separate things here: seeing the same pick often, and feeling like matchmaking is unfair. They can overlap, but one doesn’t prove the other. If you want to check whether the whole experience has changed, play a few short sessions at different times and pay attention to match quality apart from Sierra. If it still feels bad, stepping away until a balance update or a new mood is sensible. There’s no guarantee the next update will change your experience, though.