The main game mechanic is fun. Manage amassing resources , and send them at the right time. However, everything they did to try to add “deck building” or rpg-style grind and advance falls completely flat.
The VAST majority of all the cards/units you get are completely useless. You only use the top 4, and you rarely get those, while amassing thousands of minor units that can’t be sold, or used in any meaningful way. (And no, even though you gets tons of upgrade material for them, they never come close to competing with your epic/legendary units that are barely upgraded at all.)
I tried grinding for the 10 epic chests, and when I finally got there, it upgraded 3 of my 4 team cards. Great, right? Nope. The PC units apparently made the same upgrade, so it barely changed the game experience. The game a decent time-killer, but don’t waste any of your time watching ads for max rewards, as the rewards are practically useless.