Your frustration is justified, but Itch.io is only the marketplace. Most of the responsibility lies with individual creators. When you have such a problem, you should talk to them first; Fugue in Void for instance has its own community where you could complain. (Couldn't find Arkanoids, there are many games with similar names.) If your problem remains unsolved, it's always possible to request a refund via the support e-mail. But as WallaceLovecraft points out, it's usually a matter of not enough resources, as opposed to lack of interest, or worse, malice. And I know for a fact that some creators here actually own Macs and even develop on them, so their games at the very least should work.