I think a good rule of thumb is that if you learn and use framework you should understand it well enough to write it yourself. That doesn't mean you should actually write one.

A piece of technology that requires me to learn so much about it that I understand intimately what's going on under the hood such that I could re-implement it myself?

That sounds lovely, but honestly when that happens I regard it as a failure. That means its abstraction is so porous that I'm constantly having to think about what it's actually doing.

I think about the frameworks and libs where I know every iota of them... and it's not the good ones. It's the crappy ones where I'm constantly having to debug the sharp edges. "Why the heck does it do this? Ohhhhh, that's why."

Have been working on multiple project, always ended up with our own framework.

I think that's pretty common. Often it's a framework that's sort of a subset of a bigger framework.

It takes roughly the same amount of time.