The cut is too universal and not neuanced. If it was a 30% cut on profits, that would make sense, and everyone would grin but deal with it.
But if you sell something for a 10% markup, having to give that + 20% to apple is bad. And now people ask "why do I have to pay more for your service on apple vs android". And now you're in a fun PR battle.
In cases of say fortnight, there are real server costs involved. Not to mention dev costs. In cases of say music, there's licensing you pay. If you order food, you are already working in the margins.
This makes competition vs big boys even harder. How can I compete vs netflix if any streaming service I make who doesn't have netflix's negotiation power has to pay 30% of every payment. I can't get close to netflix's price.
The list goes on.
The point is, it isn't just a grin and move on problem :(