To be fair, Signal, Threema and Discord use Electron, and therefore are just crappy bullshit on Wayland.
Using a dedicated FF instance uses less RAM, CPU and disk space, and gives you more control over the application/website.

Discord has a web version, even if it doesn’t support some features, so I use it in FF. WhatsApp has a web version, so I use it in FF.
Signal does not. So it’s barely usable on my Nvidia desktop.
We do not need ““native”” Applications, made with a mix of a web version and a D tier browser engine, if we could just use the already installed, better and perfectly working browser.

• Discords Electron was outdated and vulnerable for years, FF would be patched in days or hours in case of a zero day.
• Electron uses much more resources than FF. Because every company thinks they need a custom version of electron, every app brings its own bloaty electron environment, despite there being a system one.
• Electron/Chromium is extremely buggy on Wayland + Nvidia, to the point I cannot use Spotify, Discord or Steam correctly.