well this.

when I started tinkering there were none of those kits, and the Ender I have now has pretty much nothing in common with the Ender I bought back then except some parts of the frame and the drives. and still the whole journey cost was about the same as just buying Prusa and then learning nothing.

this is a bit philosophical, but when you do want to shape material, be it wood or plastic, you have to not only understand how it's done, but to feel it. or you will repeatedly end up with crap and then endlessly wonder what went wrong

this cannot be bought, it's experience. for 3d-printing the fastest way is to get something like Ender and then build your own perfect printer out of it over several years.