I never had the impression we, the lower grades, were not welcome, or that our low proficiency level was considered as an insult to the teacher. As a relative beginner, I think even people at my level can learn lots of things at the seminars, although we cannot pick up everything the teacher shows and are often stuck with our own ways.
The problem is not beginners. As a beginner, you're not supposed to know everything yet. The problem is black belts, including people who run dojos, who not only have obvious gaps but *still* have those same gaps year after year after year... and seem to think it's okay.
All of which should matter to you as a beginner, by the way, because if your teacher isn't learning, they've set a ceiling on what they can teach you.