Largely owned by tencent afaik, putting things that are QoL and somewhat accessibility behind paywalls (like themes are a nitro only thing), do nothing against the spam bot malware thing (and they can scan the messages, since you can set the nsfw filter on them), not searchable outside of the app so things can get lost easily, their audio function is somewhat known to be problematic (for me it „catches“ the full audio out without software in between, so game sound or Netflix or whatever gets cut off completely). Those are what I can think of quickly. I am also not knowledgeable enough to accurately judge their software in terms of performance, but it feels very bad to me.