Disagree. Like any framework or medium-to-big library, D3 does take some time to learn, but totally pays off once you learn it. If you're just doing a single viz, then sure, rolling your own is ok. But if you're doing lots, and especially if they need to be interactive, I'd strongly advise against reinventing the wheel.

I also have not found it too hard to step outside of/modify the online examples, though I guess it depends on the particular viz you're trying to create.