The problem is that covid can infect places that are hard for our immune systems to clear, like the gut, and there are theories that a lot of long covid cases come from persistent infections, The frequency of reinfections doesn't help, either. China, I believe, has started treated people with drugs used to treat HIV for this reason. In the rules based international community we want to pretends it's over and isn't severe anymore and are leaving people with long covid to fend for themselves.

A lot of the new variants that show up are believed to derive from long term infections, particularly people with suppressed immune systems, where the virus can spend months mutating.