Well, they can’t, because they’re already in the public domain and nobody is around who can claim them as an original creation.

If you want this to be some pure hypothetical where that doesn’t matter, then… Sure, I guess? That’s what intellectual property is.

It’s also not a tower defense game, it’s a moba. There are towers and some defending of them, but you’re not placing and upgrading towers to stop enemies, you’re controlling one individual character from a large roster. The towers play a pretty minor role.