Fusion 360 is very much set up for a top down design approach where components are designed into a single file and joints are integrated as part of the design and feature creation process. Indeed, joints appear as steps in the timeline. SolidWorks treats mates as totally independent of the design/feature tree, while Fusion 360 treats 'mates' as part of the design process. SolidWorks and Fusion 360 approach assemblies in 2 very different philosophies. Although I still much prefer the way things are assembled in SolidWorks, I am starting to understand the way things work in Fusion 360. I am still coming to grips with the way assemblies are done in Fusion 360. Having transitioned from SolidWorks to Fusion 360, I totally empathise with you. Why is everything else in Fusion so simple and intuitive and then trying to constrain and join stuff together easily and quickly is so difficult? Did the devs just give up and think 'to hell with established convention, we'll come up with our system, so whatever, screw you' I want to fix a plate to a bit of aluminium profile, in Solidworks I just constrain it in 3 dimensions and I'm good, in Fusion I have to select points on one surface of my two mated faces and then know the distance these points must be apart in the same plane? Why do I have to do this? What am I missing? I'm lazy and want to just do it without having to calculate dimensions and offsets or know co-ordinates. In fusion I either have to build stuff together and do an 'as built' joint, or select corners and edges of my components, set them some distance from each other, or draw new sketches and dimension off those. Set your constraints and you fix parts together, easy. However one thing I absolutely despire more than anything is trying to build an assembly. As an experienced solidworks user, I've gotten on so well and have been able to design parts pretty easily right from the start. One of things I love about Fusion is it's ease of use - everything about designing parts is so easy and intuitive to someone with even basic CAD knowledge.

Fusion 360 joints