I wish that I could agree with you.
Sadly, there is another factor to this that is harder to see on the surface looking from the outside in.
I will give a rather weak, but easily accessible example here. This user pointed out an issue:
A Brief Background: In Web Dev; a coder will set a class in html, then assign properties for that class in the stylesheet.css.
With GTK, the class is set independently of the person creating the stylesheet. It is set in the gtk widget. Once set, the theme styler must work with what the app developer set as the class.
Many App Developers are taking a Very Easy Route of setting classes based on the current themes that trending which are generally flat and monochromatic.
That is a fine thing; as long as theme trends remain static.
But they don't remain static. Styles change.
And the problem is that these many app devs set classes that depend on the theme being flat and monochromatic in order to appear normal.
Instead of correcting these classes, the app devs would much prefer to Lock In Theming to prevent stylers from making new themes, prevent user control and prevent having to go back in and correct what they did.
Which, all of the above means that a change in trends won't eliminate the problem.
In fact, the app devs will probably double-down and rely on more force.
(Which, we already see them beginning to do...)