I inherited a project that would advance a lot faster if the original developers had used Bootstrap or another CSS framework.
They also chose to use an obscure JavaScript framework instead of Angular or React, so it's impossible to recruit anyone with experience, and you can't take advantage of the plug-in ecosystems.
This is a tough one. But my general instincts suggest that yes, there are significant benefits to be had from at least getting traction on figuring out how stuff works natively before adopting a framework.
BTW I'm certainly not anti-Bootstrap. It's just that suspect the tipping point in favor of its adoption lies somewhere beyond the threshold of a single form button.
By the way, do you have any suggestions for tutorials that teach someone a mental model for how CSS/HTML layout works? In particular, I'm looking for a mental model that I can apply consistently and which doesn't feel like I'm playing whack-a-mole. So far I've found that with flexbox, but I'm still finding myself in situations where I need to work with existing block/inline/inline-block code.
Not that there aren't important concepts to understand. Just that the quirks and exceptions tend to rise up from the mists, and -- just when you thought you got a handle on some particular area of functionality -- overwhelm the nice, tidy, conceptual aspects.
Which is why it has proved to be by far the hardest programming environment I've ever hard to learn.
Other than that, the hard knock school of life is my primary instructor. There's no "Code Complete" for your stylesheets (at least not one that I've found).
Should you do that if you don't already know how it works?
Form styling in a responsive, consistent, and cross-browser way is actually pretty tricky, even for an experienced front-end developer!
I totally understand the antipathy for using such frameworks, and I suggest that they're ill-suited to larger projects where you have the resources to solve these problems in a better way. But Bootstrap has it's place, and the clue is in the name.