That's a very different scenario, and a multi-decade transition. If the next MacOS removed non-App Store installations, my laptop is basically stuck in time from then on (so no security updates, no future app updates, possibly broken compatibility with my phone, etc).
They probably should be criticised if they just take you money and then go "hey, I'm not working on this anymore, thanks for the money though". If there are other reasons (e.g. ongoing costs are exceeding the money the app brings in, changes to APIs or whatever are preventing fundamental functions from working, etc, then it' might be a little more understandable). But again, kinda different from gutting core functionality from $1000+ computer.
No, because some of the small apps and tools are things that wouldn't be worth a developer's time to put in the app store. If you keep putting things in the way of getting software out, at some point it isn't worth it anymore. Look at the Safari extension debacle - Apple "improved" Safari by culling the ability to install extensions from the web, forcing devs to put them into the app store instead. Now, most of the extensions I used to use are no longer available on Safari because it wasn't worth the effort. That was an overnight change that meant I had to spend the next few days/weeks ****ing around with a handful of different browsers to find one that best fit my needs. Thanks Apple, your meddling made the experience so much better.
It's about being able to use a computer as a computer. If I wanted a locked-down media consumption device, I would have bought an iPad. If you remove any other options except installing from the app store, it's not a choice anymore. I have dozens of little apps and tools from random developers that I trust, I should be allowed to install them from the web if I want to because I'm not a child. You already have the choice to only shop on the App Store if you prefer that, but don't take away my choice to shop elsewhere.
No, but if all you're going to do is complain that people have opinions, why would you seek out a place that exists almost solely for sharing opinions.