the vaccines that did eradicate diseases did it over decades

Covid's danger, at least in my mind, isn't really the symptoms of the disease itself, it's how contagious it is. Otherwise all the "it's just a flu!" people would be right. The death rate is low, but the worry is that the healthcare system becomes overwhelmed or that specific places like a school will become a hotspot for spreading Covid. I think a vaccine doesn't need to eradicate Covid outright, just give us enough herd immunity that it no longer impacts how we live our daily lives and how our institutions function. If the vaccine is only effective for some people or doesn't have 100% uptake, that's still fewer people to be vectors, fewer ventilators needed at hospitals, etc.