I don't see what is so hard to understand.
I run a 150dpi screen.
What the problem with running a "96dpi" application on a 150dpi screen?
The text is overall too small.
What text?
Literally all the text in the entire application is too small.
What do I want?
I want to make the text bigger, so I have an easier time reading it.
Is there an application that does what I want?
Yes, Chrome does what I want.
What does Chrome do?
I set the default zoom level to 150% and it makes all the text bigger.
What text does it make bigger?
It makes all the text bigger, and the icons too.
What's the problem with Firefox?
I set the zoom level to 150% and some of the text is fine, some of it is way too small, some of it gigantic.
Why is that a problem?
I have a hard time reading text that's either too small or too big.
What's the problem with the tab bar?
It's too tall.
What's the problem with the icons?
They're too small!
This is just a you problem?
Surely fucking not. Surely I am not the only person running a web browser above 96dpi (on x11).
Is this a X11 problem?
No, Chrome works fine.
Is this a really complicated problem?
No, making fonts the correct size for comfortable reading isn't complicated.