You should 100% buy a cardboard table from Ikea if you just need a table that sorta does the job for 5 years, but if you want something made of solid wood that's a certain shape and style, you might be better off building your own depending on your product & price requirements.
Similarly there are just little things that I know can be built but there's no real demand for the product because my specific requirements are niche. For example, I have chickens and sometimes we get foxes snooping around their coop at night. I have an alerting system for this, but I'd quite like to be able to trigger gun shot noises and my sprinkler if there's indeed a fox in my garden to try to deter them from coming back.
No one's going to sell stuff like this, but I can make it. I'm also an AI doomer, so feel I need to learn basic skills like this which might help if things start getting bad and I'm somehow still around.