Cant say I've ever experienced that, been using it several years on a range of hardware types (all mac based). The UI freezing would be something local, it's not literally running every action through a 3rd party server.
Figma was quick until a 12-18 months ago, it’s been getting progressively worse. It’s excruciatingly slow at times now. The version history feature takes forever to load. It’s a shame, at one point it was, in my opinion, the best execution of a web app, having avoided all of the issues that other web apps suffer from.
I don't have first-hand Figma experience, but Adobe products aren't free from lag and freezing issues either; there's a large hardware and software surface to support that comes with its own set of issues.
It runs impressively well for a web app, but I still get multi-second freezes all the time on high-end hardware.