First, every one of the incentives mentioned in the post you replied to are CONSUMER benefits. Your comment about dropping to 5% and "all but the largest..." comment refer to DEVELOPER issues.
Key benefits on the list already exist (e.g., better purchase history management, ease of subscription management, simplified subscription cancellation). Others, like price guarantees are akin to most favored nations clauses. While not technically illegal, MFN clauses increase scrutiny and can easily bleed into antitrust (look back at the Apple Books lawsuit).
By the way, the fee apple charges is not a credit card processing fee. It also includes:
- Global tax payments on behalf of developers along with all required reporting
- First line support for application issues, including install and billing
- Support for the App Store (operations, personnel, real estate, hardware, utilities, real estate taxes, etc.)
- App Store review process and staff
- Free access to notifications servers
- Free access to use of Apple Maps in applications
- Free access to one petabyte of online storage for your apps' users' data
- Free access to Testflight and developer app beta support
- Funding for all developer tools which are free to use by all (Xcode, API, docs, etc.)
- Funding for new features in iOS and API (e.g., Metal, AI/ML, HEIC/ProRaw, Portrait, etc.)
The $99 annual fee covers:
- Deployment certificates necessary to submit apps to the App Store
- Access to developer-beta-builds of all Apple products
- Access to developer support (2 free per year)
- Access to developer forums
We can argue all day long as to whether 30% is too high. Or even 15%. But we can all agree it is not 5%. A case could be made to have an itemized fee schedule. 6% for credit card transaction processing, plus tax accounting, and a little towards developer tools funding. An additional 9% to 24% includes all the rest. And everyone still needs to pay the annual fee anyway as they will need deployment certificates just like on Mac.
edit: added Testflight and corrected a typo.