Isn't the logical conclusion of this kind of reasoning that everyone should become a programmer and browsers should be supplied in source form only, so everyone can customise any tiny detail they want to? That's not exactly a realistic prospect for most non-geeks.

User interface development for mainstream software is invariably a balance between presenting something accessible to novice/occasional users and presenting something powerful to expert/frequent users. You can go a long way to helping both groups with a thoughtful design, but there's always going to be someone who wants something slightly (or completely) different.

For mainstream software, trying to please everyone all the time is a fool's game. That's what bespoke development is for.