Like think about this logically? Should a grocery store be forced to sell my products without receiving any of the profit? Can I force a cafe to let me serve customers on their premises without giving anything in return?
Apple has no right to piggybacking off of another company's business. Therefore the 30% must go.
Compare Apple with Steam (who also provide the infrastructure, marketplace and platform). Steam don't force developers to use their services. They're still successful, but you can get almost every game on Steam from somewhere else. This is what I'd ideally like Apple to do. It wouldn't make any difference to me, as I haven't owned or developed for Apple devices in many decades, but it would make a huge difference to many developers, and many device owners. I doubt it will actually make that much difference to Apple's profits, but it would make a difference to the rapidly declining good will they have in the developer community, and increasingly in their customers.
Should the construction company that built the grocery store be able to take a cut off grocery profits and have a say in what the store is selling?