This is mainly because people who are tech-savvy already have a good set up (Firefox with uBlock Origin and all bullshit disabled), and those who aren't don't know what they're missing out on because a browser by itself (even Firefox) doesn't actually fix any of their problems.
A user-focused browser bundled with functionality that fixes today's user-hostile web (whether built-in or as preinstalled uBlock/etc) would convince anyone who tries it.
This is mainly because people who are tech-savvy already have a good set up (Firefox with uBlock Origin and all bullshit disabled), and those who aren't don't know what they're missing out on because a browser by itself (even Firefox) doesn't actually fix any of their problems.
A user-focused browser bundled with functionality that fixes today's user-hostile web (whether built-in or as preinstalled uBlock/etc) would convince anyone who tries it.