One thing I don’t like about Firefox is that its security is not great compared to Chromium. It has less sandboxing and weaker sandboxing.

Firefox sandboxing is especially bad on Android and Linux.

They they do make up for it a tiny bit with better support for ad blocking, which lowers the chance of landing on malicious changes.

Though realistically not many people care about security when choosing a browser. They use old versions and resist the prompts to upgrade.