Small pox was eradicated but it took a lot of resources and there’s been no appetite to replicate that for other diseases although we could.
This is a misunderstanding. Smallpox was eradicated, and there are about six other diseases that epidemiologists believe could possibly be eradicated.
Polio being one and lots of resources have gone into trying to eradicate polio. It has run into real hiccups however, which interestingly have resulted in significant research into how to work with populations that resist vaccination. (Hint: forcing people is not the way.)
The diseases that can be eradicated have certain things in common:
No symptomatic spread
Symptoms develop very quickly after exposure
Low rate of mutation
Vaccination completely stops the disease including spread of disease
No animal reservoirs.
It needs to have all these characteristics to be a good candidate for eradication.
Covid, by contrast, has asymptomatic spread, a period where it can be spread before symptoms develop, it mutates readily, the vaccine does not really prevent spread, and there are multiple animal reservoirs.