Hey let's make a TD with crappy animation, Disney straight-to-video-sequel art style, massive pay to win mechanics, and boring gameplay! Please, take a look at the Kingdom Rush series. If you aren't up to at least those standards, then go back and do some more work on your product.
It's fun for a once through but there's absolutely zero replay value. Unfortunately, with this sort of game it's so easy to let it sink into the rut of having only one strategy to beat it: buy all the upgrades. It goes through the same plodding grind until you boost everything up to the point where it's not challenging at all.