This is exactly the reason I would have never considered to build any apps. I have had couple of ideas but the risk is to big that a faceless corporation is going cancel your business without any reason and visibility.
Being controlled by software restricts choice, while being wiped out by software eliminates choice altogether.
So something may be an existential risk to this company or this endeavour. Only a small fraction of usage of existential risk are globally scoped to humanity.
It's kind of like saying, "I've never considered getting a job because the risk is too big that a faceless corporation is going lay you off without any reason and visibility."
The analogy would be more accurate if you could end up in a worse off position by taking the job / making the app, say through lost development time with no payoff
The risk of your app being banned when there is only 2 marketplaces is way way higher than the risk of being laid off when there are many more companies.
IMO OPs argument breaks when they equate a bit of risk to a lot of risk, as if any risk amount were the same as any other.
But the difference with websites is that there's always an alternative. If The Google decides your site is wrongthink or their superior AI intelligence flags your site for infringing on your own copyright, there are countless other ways to make your site seen elsewhere.
Let's face it, nobody's going to sideload your mobile app without installing it through an app store unless your app is in the position to say F-U to The Google like Tik Tok, Twitter, Instagram, and so on. People will visit a website that's been posted on social media or linked on some blog, but they won't download an APK.
The HN community is well aware that Google search result quality has fallen off a cliff and DDG's results keep getting better. But the vast majority of casual internet users still do (perhaps always will) use the former. The amount of people downloading APKs outside of the play store is as low as the amount of people looking up your business through non-Google search engines.
Outside of software developers, that's pretty doubtful. Judging by how many non-technical people I've spotted using DDG, I'd bet good money that there are more of them than those who would be willing to install a mobile app outside an app store. Even software developers are paranoid about doing that.
Also, the point is that at least your site can be seen even if it doesn't appear on a search engine. A business can post hyperlinks on Instagram, Reddit, Tik Tok, blogs, physical ads, and so forth. There's an option with websites. With apps, there's really no meaningful alternative unless you're a big player, and even the big players have largely bent over for Apple and The Google and their respective app stores. Sorry, the incredibly vast majority of people aren't going to explicitly turn on the Android setting to allow installing apps outside the Play Store and then install an APK off some website, and for iOS this isn't even as practical.
This really only applies to iOS.
Don't fall for the propensity of Big Tech to scare you away from general purpose computing. If you're capable of writing, testing, and publishing an app in the first place, you have an obligation to educate the public about just what the nature of the sacrifices are that are being made by accepting a "walled garden" status quo for computing.
If you're only in it for the money, that may not matter to you I suppose. If you're dedicated to trying to bring the superpower that is general purpose computing to the public however, it's one of those bits of suffering you have to navigate for their best interest.
It might be, depending on what your goals are, but for a lot of developers who just want to make a good living off of their work (as opposed to becoming a millionaire), it's not really that important.
I think you would reach a fraction of the userbase with a 3rd party process due to several factors.