The problem with that question is, that it just does not apply. I implies some arbitary restraints that offer you two choices: play this game (yours) or play another game (not yours), that somehow still is like your game, but "better". Or rather the other way round. Your game is inferiour to that hypothetical other game. Oh, and you can't play both, of course.
In reality, preferring to play that polished ww2 game does not hinder them from trying out an indie take on the genre. If they dislike indie games as such, meh, bad luck.
You are on itch. If you would take this philosphy of only playing the "better" game seriously, 99.99 of all games here would be a waste of time. Actually you could go full out Highlander (the movie), and play meta death match with all the computer games out there, till there is only one game left, the game that is worth playing, more than all the others. (You could split it for genres, and have the best ego shooter, the best rpg and so on.)
The important question should be: is your game fun to play? And it better be. Why else make it. Or rather, whatever it might be, if it ain't fun, it ain't a game.
You might want to counter ask why the most popular game ever, Minecraft, has such horrible graphics. Huge pixels. Why do people not play games with nicer, state of the art graphics? Why is pixel art popular, despite advanced high res graphcis? Why are 2d platformers a thing still, when there are 3d platforms for over two decades now? (This was to illustrate, that it is not about a game being "better")
My point is, it is pointless to compare games in such a fashion, with asking provocativly, why should I play your ego shooter, when I could play this established ego shooter that I already know?
Possible answer: Because it is a different experience. If you do not like it, ok, not everyone likes that game you would rather play either.
Now, of course, if you only made a clone of an existing game, ... asking why play your knock off, if they can play the original is a pragmatic question.
This thread makes me think about this meme. Mom, can we have ww2 shooter game? We have ww2 shooter game at home!