Haha, totally get you on the Warcraft killer comment. People don't get how much works goes into games.
We built our own survivors-like (just released our demo on Steam actually 😄), where you compose spells on a musical loop and fight to impress the audience. We started with a super novel mechanic (whammy mode from Guitar Hero and a Magicka like spell composition system), but then learning to do even just half of what the other games in the genre have accomplished has been most of the battle. 😅
Btw for your fullscreen question, I don't think there's a standard approach here. In Don't Read Chat, I did a cheeky thing and made a separate menu if the container is at exactly 960 x 540 (which is the size I made the itch.io container). So it detects if you haven't gone fullscreen yet, and tells you to go fullscreen to start the game. Otherwise, I've seen other people make their game window TINY so you have to click fullscreen to play. Or you could just make it 960 x 540, which is probably pretty big already on most screens, without being too big.