I don't think you should give up on it unless you don't feel like working on it anymore. You've already established that you are making a game different from Rock Raiders though, so why let Manic Miners discourage you? While Manic Miners has a lot of content and focus on Rock Raiders fanservicing, you have a more solid/pure coding base that performs well and is remarkably bug-free. Manic Miners has taken more shortcuts through the Blueprint system and will require some serious coding optimization efforts before it performs well on all sorts of hardware. For me to transform it into its own game and launch on Steam it'll take quite a bit of effort, effort that you've put into your game already.
I have played Mighty Miners a few times but I always find some frustrations in design decisions and in how the game plays, such as how there is almost no user feedback and how the AI appears very basic. If you'd like, I can give you a detailed feedback list and maybe a reflection on how I'd solve those issues. I don't know how dynamic your base code is though, maybe there are more problems with the programming base that discourages you from working on it.