I have to admit I couldn't even understand this problem, because for me the "stock OS" is already unbearable and I'd simply never be able to use it - I've never used it for more than a hour..

i think your opinion is pretty dated.

The issue is that of network effects. Making it harder to sideload for example f-droid makes the already small market for it even smaller, leading to less apps. It also forces people developing Apps that they don't want to reveal to be developing for completly valid reasons (Imagine developing a porn app in saudi arabia or an abortion support app in the USA) to validate against google aka the US Government.

Ask yourself how relevant and interesting you'd find this comment if someone else had posted it.