> Yes, if... But it can't. That criticism of my statement didn't make sense.

It applies directly. Anything that gives the user a choice can make the user experience worse for a user who makes the wrong one. But it also makes it better for a user who makes the right one in a way different from what the developer would have had to use as a default -- because sometimes something is right for 70% of the users, so it should be the default, but the other 30% are better off with something else. Taking away the choice makes the 30% worse off to benefit the 10% of the 70% that would have chosen incorrectly for themselves. That is not a relative advantage.

> I meant this: https://news.ycombinator.com/item?id=18583257

I'll reply there, but note that you haven't addressed my point -- other platforms survive and indeed have the largest share without prohibiting users from installing software, even when competing directly against others that do.

Nobody is "prohibited" from doing so. You want a Firefox that lets you do whatever you want, you can easily use an unbranded or pre-release build, or even roll your own or use someone else's lightly-tweaked fork. Nobody owes you an officially supported product that's for a wide audience and is also a complete free for all. Even Ubuntu and other Linux distros require you to opt into third-party software channels. You just don't like the specific choice that Mozilla is giving you, but it's still very easily there.