Due to the complexity of dealing in three dimensions and the need for output which can be interpreted by other software to create CNC or print files (for example), there are constraints on the user and any CAD package will be a steep learning curve.
I could say you get what you pay for: you would expect professional design packages such as AutoCAD, costing thousands of pounds per seat, to have had tons of development effort poured into it and to be a slick operation, but I don't know – I don't have thousands of pounds to spend.
if you want 3D CAD that is FOSS (Free Open-Source Software), there are not many games in town, so be grateful for FreeCAD. You just have to invest plenty of time getting to understand its quirks.
Everything goes well enough so long as you use FreeCAD for the entire design process. By definition, using FreeCAD tools to create a 3D model within FreeCAD's internal representation of 3D space should work! Problems start when some or all of the design is to be based on imported design elements, eg an SVG file. Then it becomes like banging your head against a brick wall.
Yes, there are plenty of YouTube tutorials on just about every aspect of FreeCAD use, and I have no doubt the examples shown work. The problem is that these "tutors" may well have managed to make it work, and feel empowered to show that off, but the process is not foolproof and the slightest inadequacy in the input data breaks it.
For example: I imported a perfectly valid SVG, but which happened to have two nodes very close together. The rounding errors when FreeCAD converted the SVG into its internal representation resulted in the relationship between those two nodes turning into a tiny zig-zag in the spline, unnoticed except under extreme zoom, but which nonetheless prevented the operations working to convert the outline into a solid object. I was banging my head against this for a whole day.
There is a great deal to understand before anyone should consider themselves proficient in FreeCAD, I'm only on the first rung.
FreeCAD Impressions
Moderator: CrazyIvan