This isn't about the user theming. It's about distros theming.
There currently is a growing conflict between upstream developers and distributions, because some of their interactions and dependencies bare badly managed.
For example, upstream maintainers see an influx of bug reports and angry users due to bugs, where the distributions are at fault. Sources for this can be changes to the code that the distributions make for various reasons like backwards compatibility, themes that break user interfaces or simply outdated packages or missing backports.
The GNOME upstream maintainers all are having their ass hanging out on a public gitlab repo, while some of the distributors, who break stuff, are very hard to find, with sometimes ancient bugtrackers.
I trust that the community will find a way to update their relationships and solve these issues, but it starts with seeing what's going wrong and where we have bad incentive structures.