Marvel Heroes. It was a diablo-clone with a lot of playable marvel characters - which you wither grinded a lot of shards to unlock - or bought them(they were expensive) -and then you grinded for skins (or bought them... Again expensive with random chance boxes).
It was cartoony, fun and easily still in the top 5 games by playtime on steam.
Rip marvel heroes, still miss ya, even if you were stupidly expensive for a f2p.
GaaS is a non started for me, but I guess the Unreal Tournament franchise got delisted and the official Master Servers shutdown. There are work arounds to get them running online, but it's a huge hurdle for possible new players.
Test Drive unlimited 2 was sadly very limited and dead for a few years now. but it was a nice open world racing game. even if I didn't want to race I would just go for s drive.
I was going to say Adventure Quest Worlds but apparently it's still alive somehow. I used to play it quite a bit when I was younger, it's a fun (albeit simple) MMORPG that eased me into the genre.
This is an old one (like around 2010), but Street Gears. It was an inline skating MMORPG that I spent a lot of time in when I was young but it eventually got shut down. I loved it and there hasn't been anything like it since.
It still amazes me how out of touch some higher ups at EA must have/still been to force Anthem to be developed on Frostbite engine. The game was cursed to fail the moment that happened. Frostbite was designed for Battlefield, not massive maps with verticality and massive monsters.
Gwent was quite generous with their free stuff and had a ton of balance changes, which might have been their downfall. The game changed a lot compared to what it was in Witcher 3, only the basic rules were the same, which made it hard for people to learn. Not having a mana/energy system meant they had to create a lot of systems to balance cards, and that made it even harder to learn.
It was a really fun game tho, and the foil cards being animated was a really cool touch.
Rocket League, still enjoy the game play, it will not likely "dead" anytime soon until they figure out how to make actual way to merge entire thing into Fortnite. (fortnite's long input lag just aren't good enough for rocket league atm)
I have not doing any other F2P or GaaS for a long time. ( does Monster Hunter series considered GaaS?)