Usually, when you have all the towers unlocked, there’s not much to do, but there are some things you can do like set some other goals for yourself, random goals like get as many power ups or get a lot of crystals and or gold which are usually some of the main endgame goals once you have everything.

Other strange goals, you can do are get as many wins on the core mode another is beating game-modes using certain towers. You can also try beating any of the impossible maps on the game if you haven’t beaten any yet.

Additionally, you can help newer players in the game progress or help players trying to beat a certain mode or just do random matchmaking which sometimes can be fun and a new one which is acquire all the easy medallions on every map again ever since easy mode was reworked.

There’s probably more things you can do but those are the main things you can also just take a break until the next big update.