You don't send a huge patch to a project as a first time contributor.
I am sure sigrok would benefit from your improvements, but sometimes the maintainer has a busy life outside the project so you need to adapt to their pace, at least in the beginning.
I think a lot of people forget that changesets are sometimes not the most straightforward way to express ideas. They (including myself) also forget that while you are working with a change in front of you it's obvious but in one month it could be opaque. A maintainer is often giving you the perspective of you a month later who built on this system you changed.
That's fine - the driver would improve if the contributions are accepted, and they don't touch core code that will break other things. But instead totally non-functional drivers are left languishing because PRs aren't merged.
In the case of Sigrok the problem didn't seem so much the maintainers, but rather non-developers "triaging" PRs with unhelpful advice to split patches, when a lack of actual developers meant they'd never be looked at anyway. Otherwise a fork might have occurred rather than wasting everyone's time.
Although that’s a good guideline, it’s not true in absolute terms. Sometimes the contribution is a big patch!