You know all of the drama surrounding Gnome and their Libadwaita? You want a quick fix? Ship apps with Libadwaita but also allow for system's theming. GIMP, Krita, Kdenlive, OBS and so many other are doing just that. Easy. If the system's theme is "broken" then users have selected that and you, as a developer, do not have to worry about them bitching about it.

Here's GIMP with their default theme:

And here it is with the system's theme:

See? Choices! And we are all happy. How about that!?