That's where I still run into problems with CSS too. However, at some point, and not because I started using flexbox / grid, CSS did click for me and now it's mostly second nature to get the layout that I'm going for.

My feeling on this whole topic is that while as a web developer I have often thought "there must be a simpler way", every time I actually start to imagine what that would look like I end up re-imagining something similar to the web stack as it is now. There is a lot of inherent complexity to GUI-based networked client-server applications that need to be responsive, continuously integrated, database-backed, real-time, etc.