Having autoimmune disorder doesn't necessarily compromise your ability to combat Covid 19 unless you are taking immuno-suppressive drugs. If you are not immunosuppressed you are probably in no better or worse position than anyone else and the same can be said for any other contagious disease including the common flu.
The need to take immunosuppressive drugs suggests exactly the opposite- that your body is experiencing an inflammatory response by an overly aggressive response to certain bacteria - not an overly weak response. Hence the very need to take immunosuppressants is on the theory that your immune system needs to be "calmed down", which would actually suggest the exact opposite of what you state- that those with AID are in a "low risk" category. However I don't believe that there is any empirical evidence that the immune system of a person with AID would react differently to Covid 19 than to other viruses they may have had or than anyone else exposed to Covid 19. I have also been told that those taking Remicade aren't necessarily more prone to Covid 19 or to having less of an ability to fight it off than those not taking it. There is no data on it. But there is no clear cut additional risk factor.
Underlying conditions can weaken the immune system of course, and an immune system weakens with old age, which is why older persons have a higher mortality rate. But just remember that most of the treatments of IBD either suppress the immune system, or else kills the bacteria that causes the immune system to overreact.
Covid 19 is a virus and it stimulates a different response from the immune system. I survived chicken pox, mumps and measles. These are all viruses and they are all still in my body and they aren't causing my IBD issues. It's quite possible that one of those viruses did cause the AID issue in the first place, but that too is unknown. I didn't develop IBD until after a severe bout with salmonella poisoning at age 9, and this is a more likely factor.