Its even worse when you force Firefox to use wayland its icon doesn’t even show.
Edit: Oh since everyone now is confused; I only have the flatpak version of Firefox installed yet it doesn’t use the pinned icon and doesn’t even use the firefox icon under wayland at all.
Since when is theming aaccessibility? That’s customizability.
But you can have your wishes easily. If you prefer no Linux support over an Electron app, just don’t install the Electron app and you get the same result.
Consider yourself lucky that you are not visually impaired and need high contrast and/or large themes.