Again, you’re misunderstanding the problem. Keeping applications up to date is not a problem. Keeping things working the way my family got used to is an entirely different matter, and it’s actually worse on Android & iOS (thus, most phones and tablets).
The main reason the family even has desktop PCs is because we couldn’t make tablets work for them. Something as simple as reading email was a problem, because the various email apps (gmail, k9, etc) changed their UIs, confusing the heck out of my parents. It would’ve been possible to improve that situation, but the tooling to remotely manage an android phone are far more limited than on a bog standard Linux desktop.
A lot of people do use phones tablets as their main computer, yes. Ask them how happy they are about it, how much trouble updates and random UI changes cause. Just because they “can live with it” does not mean they enjoy the experience, or want to live with it. Chances are, they don’t have other options. My family does. I think more people should have those options available to them.
(Also, the blog post is about desktop, specifically, and is a critique of distros trying to aim at non-enthusiasts. When it comes to mobile, those efforts are even more futile, because those specialised distros will have absolutely no chance of working on anything but a very tiny subset of mobile devices.)
Building a browser engine is hard, especially when the target is moving at a rapid pace, and that target is controlled by Google. Like it or not, the web as it is today, is pretty much driven by Google (and to a lesser extent by Apple and Microsoft) these days. They can throw infinite resources into developing the browser engine and the browser itself. The closest competitor we have today is likely Servo, and they scrape by on pennies.
Developing something from scratch, with even less funding and expertise than Servo is a non-starter. It’s not going to happen. Sure, sure, there’s LadyBird and some other independent efforts, but I very highly doubt they’ll ever catch up to the three major engines.
To develop and maintain a browser, you need people, and they need to be paid. Paying open source developers is… quite a big problem in and of itself, even for things considerably easier and smaller in scale than a web browser.
They would not, because for every developer who would do this, there’s 100 who would not, because their livelihood depends on people with Google browsers being able to use their stuff. Google is in a position of power here: they are the #1 search engine, they are the #1 browser, they’re pretty well positioned on the mobile phone market too. The vast majority of businesses (companies or individuals, doesn’t matter) simply can’t afford to go against Google.
If the vast majority would, then yeah, Google would backtrack. But that would require a coordinated effort, from the vast majority of the internet. Likely multiple months of protest. That’s not going to happen, people can’t afford it.