There is also the issue of surveillance. Apple processed warrantless FISA surveillance orders for 30,000 users last year, per their own transparency report.
It's possible that people don't want Apple (and by extension the FBI and US military, with no probable cause or warrant required) knowing the apps they purchase and use, or when, or on which devices.
Being App Store only prohibits that, and requires that your users be subject to this surveillance.
It's the same issue with posting to Instagram, for example: deciding to donate free content to Facebook there makes the product more attractive to Facebook's users and makes it harder for small businesses to opt out of using Facebook's ad business. Decisions like this make the whole world worse.
During a software license purchase for macOS, you either need to provide your PII to Apple, or to an indie developer.
In your opinion, is it safer to provide your PII to an indie developer than to Apple as part of such a purchase?
Assuming that is the case, is your objection to Apple having your PII then extended to all other large-volume payment processors such as Shopify, Stripe, Amazon, and PayPal as well?
(Please don't let the downvotes stop you from expressing these views again and again. You are not a minority on this.)
The App Store might be safe and all, just like Disneyland is a safe place for kids, but I personally prefer the real world.
Consumers go where it's most convenient, and sellers follow them. Anything else is wishful thinking at best.
Objectively that isn't the Mac App Store in general, thankfully Apple's incompetence in the user experience has held them back in further damaging society by centralising application installation further.
You can't download even free apps from the App Store without providing an email address, phone number, and street address (to get an Apple ID). The App Store app also sends the mac's hardware serial number to Apple when you launch it, associating it with your identity in the logs. The email and phone required are verified so you can't just make some shit up.
This means that to get any apps from the App Store, even free ones, you must be thoroughly de-anonymized.
Not caring about privacy because you have nothing to hide is like not caring about free speech because you have nothing to say.
Developers should reject the App Store on customer privacy grounds alone. When this becomes the sole method of distributing apps on the mac, as it is on iOS, the world becomes a much worse place, as then the US government had permanent access without a warrant to every app you use.
Please don't contribute to building that world.