My only issue is really the uneven application of the rules. Creating these loopholes to allow major streaming services to push users out to sign-up, but not allowing it for other apps. I would be in favor of a scaling rate based upon downloads/sales, with less percentage paid at greater volume, to encourage these signups to be in-app, which improves the experience and makes the platform costs more "sustainable" for apps with strong growth.
Of course, no one really complained about the 30% when the App Store first came about, it was considered "fair" for the overhead and for providing the service. Granted, time passes, standards change, rules are applied unevenly and it's all confusing. Others have stated the Amazon publishing cut being very similar.
That 30% would have to cover the obvious I&O costs of hosting and delivering all of the software, but also cover the notification systems, offset the I&O cost of the substantial number of free apps, the staffing for review and customer care, and the credit card and chargeback fees. It's non-trivial costs, they're probably not netting a truckload of actual profit out of it.
Maybe they could shed a third or so of it (going down to 17-20%) and treat it more like a break-even business, but it's probably not a simple thing to do. I'd say there's a laundry list of expenses against that 30 cents on the dollar.