Grinding gear has nowhere near 500 people. The latest glassdoor posts say between 50-100, they posted themselves that they employ about 100 people a little while ago (some positions are part-time).
But yeah you can't really compare the 2 games.
PoE NOW has 100+ppl, but back when they released, it was a small company(they had 25ppl during the open beta, which was the "soft launch"). And the released state was a lot better than this, probably because you know, they ran a beta with all the content for years before that, instead of just throwing a complete rework live and expect things to go well.
And ultimately it's still a poor argument to compare a new game releasing to a 5+ years old game when it released. You can't excuse everything because a game long ago had similar issues. People did that shit constantly with mmos too, "oh but remember wow at release it was such a disaster" like that somehow excuses a game 10years later having the same issues, like the tech is the same and no one can learn from previously done mistakes. And I'm not necessarily talking server issues, that shit's messy especially for games with larger success than expected(which this did have).
Big issues like server stability, stash being deleted/not accessible, gold dupe and so on aside, there's a ton of massive balance issues in the current state of the game. Basically you can't make a good caster or summoner(which is pretty much a joke), it's only ailments or weapon based characters. Even for weapon based characters, there's massive discrepancies, for example anything with a shield is going to do 3 to 5times more damage than anything without, because of the busted shield passive. Difficulty is super spiky with almost nothing being threatening until you lose 80% of your health in one shot to some rare mob(that's similar to poe btw, it's shit in poe too though). A very very large amount of passives are complete shit due to terrible decisions like additive damage on everything but also giving you a stupidly high number of base damage% via stats, so anything that's like "+20% fire damage" is absolute trash, and that includes any % on gear, making flat damage the only thing that matters.
The pacing of the game feels off too imo, with trash mostly dying instantly ala poe, but then the density is garbage so you spend more time travelling between packs than fighting and the packs being too small most of the time so it doesn't feel rewarding to kill them either.
Ymmv obviously and some people definitely enjoy the game, personally I don't think it's worth 40bucks in its current state, I'd wait for a sale.