Your answer isn't exactly wrong, but it's painting with a broad brush. "immunocompromised" is a broad term (even more so than "immunosuppressed"), so there definitely are people who are immunocompromised who could potentially benefit from a vaccine (again, we don't have hard data on that yet for any of the vaccine candidates and won't for a while).

They do help indirectly - by innoculating the 90% who can take a vaccine, the 10% who can't (for example babies when it comes to measles vaccines) are unlikely to actually catch the disease.

Oh, for sure, I wasn't trying to say vaccines shouldn't be used! They are extremely important to a healthy population overall, and it is all the more important for people with healthy immune systems to get them to help protect those that can't benefit directly.

Transplant recipients (which must be on suppressants for life) can and do take vaccines and they work. They generally can't take live virus vaccines, but that's about it AFAIK.