Long Covid has so far been shown to cause a number of serious issues including heart, lung, or kidney damage, type 1 diabetes, and blood clotting issues. And we still have much to learn about it.
Experts estimate it's affected around 10%. A significant proportion of the working age population. Many young formerly fit and healthy.
Note that's with some form of restrictions. Who knows how many more might develop it without.
We also don't yet know about potential hidden problems, i.e. damage that only becomes apparent later on life.
Those who still scoff at it's existence. The cash strapped NHS does not made a habit of setting up treatment clinics for non existent illnesses. Perhaps also have a chat with the group of doctors who wrote to the BMJ describing their personal experiences of it's debilitating effects.