Depends. If I'm working on a team project and others are using a framework, I won't exactly tell them to stop using it. Similarly, if I'm lazy/don't want to worry about design, well Bootstrap will probably get me a nicer looking site than anything I'd be able to come up with on my own.
But if it's possible, and there's a designer willing to create designs for components, then I'll use CSS Grid and Flexbox without a pre made framework.
I've found that when you reach a certain degree of complexity in an application, a functional CSS library like Tachyons (http://tachyons.io/) or Tailwind (https://tailwindcss.com/docs/what-is-tailwind/) is the only sane choice.
Don't use grid, the main thing I'm working on has hand-made CSS (with a mobile first layout (with some sizing for larger display) https://doplaces.com
On another I'm just getting into - working on a simple one/two column thing (large screen two block columns, small screen goes to one some text/image scaling).
I find a lot of CSS frameworks are over-engineered, and with addition of various modules and tools adding redundancy to a site's CSS soup.
I can see a lot of refinement can be made by paring out CSS parts into several sub-classes and then mix them together in the element class assignment (I cant say all my stuff is like that yet, but that what I'm striving for.) I'm just getting into front-end so I'm learning as I go.