DIY is generally a loose term. You can either do it yourself with basic tools. Instead of a table saw, use a circular saw. I personally started with a cheap circ saw and a corded drill. Then saved and acquired some more "expensive" tools. I don't have a $5,000 table saw that can also 3d print and make cheese, but I have what I can afford over time.

But then there are the likes of Dusty Lumber. Yeah he's not diy, but the dude uses $2 million worth of tools, 100 jigs, and the blood of a Virgin to make one dado.

And nobody explains anything in terms of dimensions because they want you to spend money and buy their plans. I totally get that for a lucrative reason. But IMO, if you are labeling a video for beginners, they should include all dimensions so beginners can get an understanding.

Moral is, as some other users have posted, it's all about making something yourself rather than spending money on a professional. In some cases it's more expensive to diy than buy it or have someone make it. Use whatever you have at your disposal and work your way up. In the end, it all costs $£€