Proper constraint-based drafting is indeed quite hard! But I think the whole "lay out this 2D grid-like structure with a few rectangles" problem is probably one of the first things anyone would learn to do with it, and I'd submit that it is indeed probably about a couple of hours' work, for someone already reasonably technical. The moment there's more than a single sketch involved, or complex geometry in that single sketch, I agree with you that it's asking too much.
The real benefit is that you are starting to learn something new. CSS is not going to help you (insane contortions aside? I really don't want to find out) when things like circles appear. And yet, if you know how to do 2D sketches, you can find yourself using them to solve other problems, just because you already know how to do it. And that's pretty cool! (For example, I've had living rooms that were just awful to lay out. It was a real nightmare to figure out how to get a TV into that place. So I sketched it up and messed around until I got something viable. My original plan was just to print out some pieces of paper to scale, then mess around with those, but it was soon clear I could do it all onscreen, so I did.)
It can export to SVG, DXF, PDF, GCODE, and more
I'd also submit that it's of limited value if you aren't using the same package as your shop. The browser-based method is at least all but guaranteed to be available to the people building the cabinets.
Since they'll have to do shop drawings anyways, you aren't gaining much even if you can interchange drawings with their CAD software.