They basically turned the game into a testbed for extremely exploitative practices. It's been a while since I walked away in disgust, but one example I remember is the crates system.

Essentially, they added "item drops" called crates. These crates do absolutely nothing unless you spend $2.50 to buy a key to open them with. It's basically an extremely insulting lootbox model.

Aside from turning the game into a hat simulator, they also introduced loads of game-breaking straight upgrade weapons for you to grind for, and continually piled them on over the years, often just taking community-supplied models and slapping stats on them. At some point they even tried to add full sets of expensive cosmetic items that would give you straight stat bonuses when worn, which even they had to back down from.

I've never seen more aggressive monetization while ruining the base product than I saw Valve apply to TF2, hence my surprise at your impression that Valve wasn't capable of money grubbing. In the case of TF2, they were somehow actually worse than Activision-Blizzard.

Hahha that's exactly like Counter Strike:Global Offensive (which I do play). It's definitely some dark UX/a manipulative practice, but well within their rights to do, as long as the stuff that comes out doesn't actually affect gameplay.

Breaking the games balance with pay/gamble-to-win stuff is pretty shitty IMO though, yikes.

Now that I think about it, Counter Strike: Source didn't have any of the crate nonsense or skins... Yeah they probably learned that from TF2.