It seems like a reskin of a game I've played before, or perhaps a combination of two I've played, but the general gameplay is pretty good so I'd normally give this a high rating. However, I've got a few bones to pick, which I consider pretty serious:
Firstly, the upgrade system seems to be borrowed from the game that was copied, but without much understanding of why it existed: you just seem to keep the money you gained, and any equipment you bought. The game I recall this being either based on, or ripped from, you gained levels to increase your starting money, so you'd inch your way forwards, while still being able to buy up your characters during the game. The structure of this still exists, but without much of a point. How did this happen? Is this literally stolen or copied code?
Secondly, the two slot system is rather unreasonable. Either someone has to ditch their gun to have speed or loot upgrades, or the upgrades which don't have armor are going to be on 1 health characters who die in a single shot. I'm not even 100% sure you can even ditch your gun, which means speed and loot aren't reasonable upgrades later on.
Thirdly (and this is a big one) I appreciate that having ads in your game is something some gamemakers need to do, and I'm fine with optional ads that give you a bonus that isn't necessary to complete the game, but just make it easier. But allowing you to continue after a death with ads takes all the challenge out of the game, and I find it VERY scummy that the last level has completely unavoidable lasers so that you HAVE to watch ads to finish the game. I'd have scored this game significantly higher if it weren't for this fact. You've made your game way worse than it could have been by selling it out.
Even if this game using some code, or at least ideas, from other successful games, I still appreciate that work went into making it what it was. This wasn't some cheap cash in, someone spent some time on this. But making the game unfinishable without ads is beyond the pale, and I can't forgive it.