Squarespace really sounds like a nightmare, and also very rough on people who work a support/call center role rather than a dev role. I say this having experience with both, as only the call center involved handling tickets as a primary activity, and having a regular night shift (rather than being on-call every few months).

On the other hand, this sounds pretty grandiose to the point of being delusional:

"Squarespace, you hoped I’d be another black woman in the tech industry who would quietly watch as you grow in power while I wither away. You are mistaken."

Squarespace: a company actively dedicated to the withering of black women in tech. That's a pretty extraordinary claim, so it needs some pretty extraordinary (ie, non-anecdotal, verifiable) evidence. The adjectives used to describe literally every other person in the story are mostly if not completely negative, and this ultimately weakens the writer's claims.