No, you want to remove the clippings. The soil needs to be (or become) nutrient poor if you want wildflowers. Otherwise, you just get grass, which is no use to pollinators.
When one wants strictly a meadow, then you're probably right. I'm doing that in a garden for a decade or more, and we have a mix of grass and wildflowers and "weeds", with abundant biodiversity.
I mulch and it is perfectly adequate for promoting dandelion growth. I don't have "wild flowers", but plenty of daisies, dandelion and clover.