Duke of Defense
I had to buy Duke of Defense twice. I got it on Switch because I wanted the portability and thought I could simply purchase the soundtrack via Steam, but Steam requires that you buy the game in order to download the soundtrack. Boooo.
The core gameplay in Duke of Defense is fine, which implies the non-core gameplay sucks so let's get that out of the way up front. First of all it's too easy to accidentally sell your towers when you're trying to upgrade them. Second, the more advanced towers are overpriced and underpowered and practically useless, so you're best off just sticking to the basic 3 towers types. Selecting which tower you want to build is also a bit troublesome with the analog stick. Finally, the unskippable cutscenes are unforgivable. Just patch all this up and everything will be cool.
Multiplayer is where Duke of Defense shines. The tower defense / action hybrid bodes well with the management / combat strategy, and hooking up with a friend to take down enemy waves is a pleasant experience that provokes communication but is never overly serious. Speaking of pleasant, the soundtrack by Christopher Anselmo overachieves. I'll be keeping an ear out for his next project.