That's because I wont pay Apple $100/year for a dev license. You can either run a console command to disable the check, or run the game via the Itch launcher.
For a year, perhaps. But you also have to consider that I'd have to buy a Mac which raises the cost considerably, and the time/effort cost of me learning how the process, then repeating that process for every update.
This creator is far from the only one to take this approach. It's part of why indie Mac support is so sparse. Apple is user-friendly--not dev-friendly.