It's missing containers and overall has less privacy features available than firefox.

This is exemplified compared to forks like librewolf that enable the majority of them.

Ungoogled Chromium and stock Firefox are pretty similar privacy-wise though.

The main advantage is all baked-in telemetry is stripped out, but it doesn't do much to protect you from privacy-invasive sites other than disabling WebRTC and blocking 3rd party cookies.

I used it for a number of years, but recently switched to Librewolf ~5 months ago and don't expect to switch back unless Firefox and all downstream forks completely implode.