This is fine so long as someone doesn't open a low cost app store that doesn't screen apps and only charges 5%, causing developers to flee there en masse, leaving the first party app stores devoid of content.
It seems the hyperbole on MacRumors concerning this topic is evident.
1. May you support an open and free market to install apps directly from the developer or a 3rd party vendor similar to MacOS/WindowsOS/Linux/AndroidOS/etc is the end users free choice regardless which OS developer and device is being used. Don’t want to install app outside the official AppStore that’s fine, no one is forcing anyone to do so. Similar to MacOS the end-user has a choice to install from the MAS, directly from developer or 3rd party stores and mirrors.
2. It seems the supporters and Apple are concerned that if the individual developers are permitted to allow their apps to be installed on iOS/MacOS (Apple Silicone) devices that the AppStore and MAS will be rendered irrelevant. Why pay the annual $99 developer fee and have Apple take a 15-30% cut from your revenue when a developer can host the iOS/MacOS (AS) app on their website under their own terms and conditions with competitive payment methods along with less restrictive measures. If a developer has their app/s on the AppStore/MAS/PlayStore/etc why have these platform stores take a percentage cut when the developer has to have a website too (not always but preferred for marketing purposes). I believe supporters of the AppStore know that if the AppStore and others are opened the developers will abandon it overtime and that means eventually the AppStore will be irrelevant. It’s a financial based interest for Apple, it’s shareholder and people with an AppStore balance.
3. While the AppStore does provide some benefit of advertising and transparency for vendors for example privacy nutrition labels for minimal cost, some vendors resorting to user data harvesting do not want to conform and respect user privacy. The cost of advertising also goes up as there is no single venue for user discovery.
4. If a reputable developer hosts its own iOS/MacOS (AS)/AndroidOS/etc, it maybe have flexibility to lower the cost of its software due to reduced transaction fees and no developer fees, it may also mean less or no subscription software.
5. I believe Apple has an opportunity here, rather than fight change the very thing it aligns itself with such as Environmental Sustainability, Human Rights, etc it can demonstrate to developers and users that rather than have a sole website the AppStore can be the developers website and host iOS/MacOS (AS)/AndroidOS/WindowsOS /etc. One single store, developer pays an annual fee for hosting and permits the developer to offer either ApplePay/GooglePay/SamsungPay/3rd party system.
6. These changes may sound absurd to host competing platform apps for one developer but in reality it demonstrates to the end user that Apple is willing to walk the talk and open its AppStore not only to other companies software being hosted but also payment and support systems possible incorporated via some plugins. Have the AppStore as a service a single point for developers to host all platforms their choose and not have to publish their software on AppStore/PlayStore/Amazon AppStore/etc. Plus it will be a big win relating to antitrust mindset. This one change will be a big boon to its share price and Apple can extend the benefit to offer verified iOS/macOS/AndroidOS/Amazon Apps/WindowsOS/etc under one AppStore with verified and unverified clearly illustrated and opening up the system with a complete rethink vice fighting this wall garden mentality. Innovation through partnership!