I imagine a lot of the reaction here is because Coscos are generally absolutely massive stores that sell everything on earth usually located some ways away from anything at all surrounded by giant parking lots. Building apartments atop large stores in a city is extremely normal.

I think the only thing you're missing is the pessimism that the only way these will be implemented is in an overly exploitative fashion.

Having mixed-use buildings with residential over commercial properties is very common in the US as well. I think the base assumption leading people to the pessimistic appraisal of the project is that Costco will be the one renting the space from Thrive and subletting to Costco employees among other renters similarly to historical Company Towns. I haven't yet read anything to confirm or deny this assumption.

private capitalist enclaves just have a bad vibe, also it's like a combo of all the bad/annoying parts of the collapsing west rolled into one - your landlord, HOA, your boss, all the same inscrutable entity, you can't advocate for yourself in the workplace without risking your housing, and you can't fight a shitty landlord or HOA ordinance without risking your job.

Also just further atomisation and alienation, people living at the remote megastore instead of leaving their street to go out for essentials.

Also now all your co-workers are your neighbors too.

Those are the things that come to mind.