FreeCAD’s UI is good enough to work, but not to everyone’s taste. Personally, I detest the clown car UI of Fusion and it’s lack of customization for my work flow - custom pie menus rock. Something that FreeCAD allows the user to do. Not to mention the half-assed mix of local install/cloud that is Fusion360. It locks your projects in the cloud subject to AutoDesk’s whims, but eats your local storage. At least OnShape and TinkerCAD is all cloud and honest about it. But it’s all pay to play if you want access to the good stuff.
They are improving the FreeCAD UI slowly. The Ondsel version, (based on the 0.22 Dev release), gets high marks from a lot of users about the UI design. Not my personal cup 'o tea, but I do see the allure for many users. Besides, if you don’t like how it works, you can easily customize things to your personal tastes.