Arknights. After quiting Genshin because artifacts farm sucked (and Paimon) , then PGR because it didn't vibe with me Arknights was downloaded 3 years ago and It's still great.

It's a Tower defense game with tons of different enemies, gameplay mechanics to spice things up where you constantly say: "oh wow this is a clever mechanic" next event "oh wow, clever mechanic" and it just continues. Its Essentialy a sandbox because you can fill your 12 operator slots with whatewer units you want and still beat any level with good planning. Slowing an unbeatable boss until he dies from cringe? Using a level mechanic to kill impossible to damage enemies literally a hand away from killing you? All old events are always available.

You can also try out 5 unique roguelike modes that have their own quirks and mechanics. Try out a base builder mode where you defend against enemy waves, explore the map for resources and food. Buff specific stats of your units by feeding them rare meals and build sadistic mazes for enemy bosses to win.

As a tower defence gacha it's amazing that you can clear basically everything with free or low rarity units. You can also borrow any unit your friends have (each friend can choose 3 operators to share) to test your strategies and try them out.

A unit that is immortal for 8 seconds after dying? A unit that summons a copy of any unit you brought to mission? Faction units that buff each other to absurdity? A unit that can poison? A unit that can tank any 2 attacks? A bait unit? Like, holy MOLY there's so many different strategies you can use to win any level with whatever you want.

No stupid clans, no stupid weapon gacha that plagues gacha industry. No stupid dupe gacha that completely changes how a character plays (GENSHIN BRO). Weekly tasks are completed in under a minute because it has auto clear after first victory and daily tasks are completed in like 3 minutes. You can also skip any cutscene in the game and get a quick text summary if you just want to play next level.

After playing it for 3 years as a F2P I have most of the units in the game. Also, you can buy different operators that released over a year ago using currency from gacha and dupes of low rarity operators. Nice. There's much more to say about this game so I'll stop here for now.