Just can't get good at building?

I would suggest you start recreating houses from google cause that way you really start to learn using all of the sims 4 build features and you also start to see what looks good and what doesn't. This is what I did in the beginning and I have improved a lot since my first builds. I would also suggest that if you don't have quite the experience yet, you stay away from diagonal walls for a bit since the roofing on them is indeed a handful. You can always find me on the gallery under simooon2002 where I have recently picked up uploading builds again so feel free to ask me any questions there if you have any!:)