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.
You aren't owed a native package for whatever OS you're using. In fact, you should be thankful that flatpak exists because the most common alternative is piping wget into shell.
And if you care so much about security, just build your stuff from source. Whether flatpak or apt, at some point you will run third-party code.