1. First several 3-d design iterations are throwaway reworked because I am constantly measuring the design, clearances and studs. And paper works best here instead of working with clankers which takes way longer.
2. Choosing the right kind of materials: thickness and type of plywood, type of hinges, panels, finished or unfinished. Optimize for simplicity of putting components together is most important.
3. Once the design settles the actual joinery needs to be as simple and efficient e.g. butt joints work well most of the time. A good jig for pocket holes is generally the most needed. You will be surprised how well a staple gun works for creating back panels of cupboards.
Its not that they are not useful, shopspec looks great(good job variodot), its just that I can get further and faster without them for most hobbyist pursuits. I invoke YAGNI most of the time because I constantly ask myself one question: "How can I make this be less time consuming?".