I don't know why custom elements never became common knowledge. I've had PR's blocked by people convinced I was doing arcane black magic by using them. But the

I don't know why custom elements never became common knowledge. I've had PR's blocked by people convinced I was doing arcane black magic by using them. But they've been worked this way for decades. Now they weren't officially added to the spec until browser support for v1 of custom components, but that was still back in 2016.