Making graphical software more unixlike

NetBSD works good on the RPi boards. The support for that hardware is in fact much better than basically all the other ARM boards. See here:
wiki.NetBSD.org/ports/evbarm/raspberry_pi/

Myself and anyone with a LAMP stack would like to have a word with you.

Which is exactly what you want on a large enough project.
You don't want to rely on the OS unless strictly necessary, so you aren't stuck on a suboptimal OS as easily.
Imagine coding something that relies on the X server and then having to redo it all when wayland becomes virtually mandatory.

Lisp machines are a funny metaphor for communism. :^)

A software library is a library of software functions. When you have multiple libraries that are conglomerated to form a big cohesive library spanning a wide range of general software functionality, this situation is often referred to as a software platform. It is very normal for programmers to target specific software platforms rather than to recreate a targeted subset of what a software platform provides. When your software targets the X11 protocol, that is a design choice that the programmer makes. If the team decides for the program to target the Wayland platform, that will take significant effort. However, I would bet that this effort is smaller compared to the effort required to independently implement the tiny subset of needed functions that are offered by the X11 platform or the Wayland platform.

As someone writing software, you are interested in minimizing the amount of work you have to do. That's why you probably prefer writing webapps over real applications. As a user, I prefer software that uses familiar idioms, and integrates with the rest of my OS, so that it minimizes work for me. As such, I prefer software that is a library first and foremost, which works completely independent of the OS, then has a layer of UI code surrounding it to help me get my work done. Besides allowing for the application to be ported between OSes, this allows someone to consume the library directly in their programs. They could even write their own custom ui.

I believe he would recommend that you use some framework like qt or electron rather than target the windowing system directly.

Sure, because most programs don't have the requirements an IDE is expected to offer nowadays.
If my game has a tiny difference in chat text formatting between Linux and Windows, that's unlikely to even be noticed, while an IDE formatting text differently on different systems could be a big source of headaches.
Combine that with the extreme portability demands, and forking your own solutions starts to sound good.

I can't say writing webapps is a pleasant experience, especially since performance requirements bite you in the ass as soon as you try to do anything interesting with them.
Which is general a wonderful idea, it's so good even the most webshit IDEs follow it by having some impressive internal modularity: of course they try to lock down user-facing modularity so they can jew you out of money for dark themes and such.
Also, I would only recommend electron to my worst enemy, and even then only if they really pissed me off, qt is pretty neat tho even if you were developing only for windows.

YOUR JOKE HAS GONE TOO FAR
github.com/lllyasviel/style2paints/blob/master/README.md

that seems pretty cool, and a good example of sensible modularity as it's based off real life workflows.