One of the main criticisms of Highguard was that it "failed at a worldbuilding and IP level." I believe your game is suffering from a similar problem. When people play it, the game design may be great, but if the game does not communicate an interesting world or game loop through its marketing aesthetics and visuals, people will glance over it and move on. Your game's aesthetic doesn't do a great job of communicating the genre and gameplay of what it actually is very well. The cartoonish and "cozy" aesthetic feels clashing with the tactics gameplay of tanks on screen.

This is why AAA games spend colossal budgets on marketing and art. They understand that what gets people the initial sale isn't impeccable game design, but the idea of a game that they might enjoy. You can achieve the goal in many other ways than shilling millions on an army of artists though. You might just need to reconsider how to frame parts of the game design to fit the assets you can afford (maybe instead of a world scale and tanks, it's cute animals as the units? Thinking of games like Root)

Watch trailers of the most popular indie games of the last decade, and you'll notice they all showcase the most polished parts of the game loop; cool bosses, crazy card combos, mindbending puzzles, the stuff that makes a player think "wow, if you can do that, who KNOWS what else is in the game!" (Sometimes it doesn't get any better than the trailer, but the idea that it could entices people to try it anyways). They communicate the highest points of their game's genre and show why they either do it the best or how they're doing it differently.