sketchup ?

@Jim Welton - Not to jump on the "Dave Richards is the man" wagon but, he is. I was exactly where you are years ago and was fortunate enough to get some help from Dave. Within about 20 minutes I went from frustrated to that "ah-ha" moment when things click. My fundamental stumbling block was having worked in 2D for so long that I couldn't wrap my head around the idea that I was looking at a 2D screen but working in a 3D space. Once that clicked I was off and running.

I am not and never will be a SketchUp pro but it has become really irreplaceable in my design, planning, and detail work. I would strongly recommend Dave's Sketch Up Basics course at a minimum along with his many Fine Woodworking online articles and videos. Despite having been reasonably proficient for years I do not possess many advanced skills but, I do not need them to get a great advantage from the tool.

I will add that while watching the training videos I get as much from "how" things are being done as I do from "what" is being done. Keyboard shortcuts, control, shift, and alt key functions, selecting from the left versus the right and so forth. I run SU 2017 in Windows 10 on a moderate system with a stout video card and monitor and get by pretty well.

P.s. Hi Dave :)
@Jim Welton - Not to jump on the "Dave Richards is the man" wagon but, he is. ...
My story is much like Glenn's. I had used a 2D system (Visio) for business technical drawings for years. I tried SU, but stumbled around not getting anywhere. Then I met Dave online, got a bit of instruction and the rest is history. I'm far from being a pro user but get cabinets, etc., drawn just fine on SU2017 on Win10 and Win11.
Same here on the 2D. Used visio and loved it. At first I was trying to use sketchup as a 2d program, but something clicked. Mostly it had to do with figuring out how to get a cube, or a board modeled and from there it just became second nature.

I'm nowhere near Daves skills, but I manage to be able to draw most things I want to 3d print with sketchup quite easily. I've tried to get into other more technical cad programs, but I seem to always be able to do what I need to faster in SU.