> Maybe because I'm from a different era, but installing anything on a device from a website is an extremely risky game

You are (just like me) from a different era. /s

I was trying to compile rust (for mozilla) and i was shocked to see that it connects to the internet during the build process to download crates (i presume these are some kind of libraries). Then you have js with npm and the menu is served.

Even if the web browser has a container, this can be compromised during the build process.