I was curious about the negative reviews and skimmed through many of them. I made a sum up of most of the complaints, roughly in order of prevalence (only english reviews)
>bots
>microtransaction are evil (paywalled customization)
>bad netcode/ping
>matchmaking (and free rank lifting)
>balance
>no linux support
>no mods in pvp, no functional reward (like playtest)
>game is actually pay2win
>game not intuitive, cluttered (bad UI, tutorial)
>I don't like extraction shooters

some singular complaints
>I hate mashmak
>Cashshop bug, refunded credits, resulted in ban
>horny character creator
>AI voices
>characters are actual ugly

I also looked through a few some chinese comments with translator. From what I understand their complaints are quite similar, a few more mentioned lack of content, but it is hard to decipher them.