We’ve ended up with our own, not so much a framework but a set of commonly used mixins and set of SASS files - some of which might even be empty placeholders - that stop us trying to work out the same issues over and over.

I treat it a bit like adding packages with NPM, just adding the small bits we need to achieve certain things.

When I’ve tried to use proper frameworks before they have always been too opinionated and I would find myself working around them.