I have read through it. I just vehemently disagree that their requests are reasonable.
The only reason why people care so much for their apps' "branding" is being enforced by product management. Absent that pressure, you get a reversion to the Windows ecosystem pre-2005 (more or less), where every user can make their desktop as nice or ugly as they want, and by and large, the sky isn't falling. Because everyone works with the platform and tries to fit into it instead of breaking the mold.
One thing I really hate about electron apps (besides performance in many cases) is the extreme branding they do. Every app looks differently, not fitting in with the rest of OS.
As a user, theming is a powerful feature to make things look somewhat consistent.
Though I use KDE and Qt apps as preference, and very few gnome apps. They tend to cope with this pretty well.
As some who normally uses GNOME, I actually like apps to have distinct visual identities so that they are easy to tell apart at a glance. When using VSCode or Chromium I prefer their native title bars and modal dialogs, which integrate with the rest of their appearance, instead of the grey system-provided widgets.
I can imagine.. But everything about GNOME rubs me the wrong way, so I find it hard to compare. The huuge title bars even when I don't have a touchscreen, everything hidden under a hamburger menu, the lack of configurability..
So for me the comparison against KDE is very different. KDE's tools have pretty sane defaults and can be customised very well.
Who's “product management” in this context? Most of these apps are just made by one person.
Again, this letter isn't about users making their desktop nice or ugly; it's about distros applying stylesheets to apps without checking whether the app remains usable, and leading users to expect that this is the app developer's responsibility.
The only reason why people care so much for their apps' "branding" is being enforced by product management. Absent that pressure, you get a reversion to the Windows ecosystem pre-2005 (more or less), where every user can make their desktop as nice or ugly as they want, and by and large, the sky isn't falling. Because everyone works with the platform and tries to fit into it instead of breaking the mold.