Why not? We eradicated smallpox.
The MRNAs are non-sterilizing, as are many vaccines. They may reduce symptoms, reduce infections, and reduce transmission, but they are not considered a sterilizing vaccine.
Secondly, coronaviruses mutate much faster than smallpox, and have other hard to deal with stuff like asymptomatic transmission.
The only diseases we ever eradicated were polio and smallpox. I think we got rid of the guinea worm too. Out of all the many many diseases we have fought over the years.
The vaccines we have are non-sterilizing - and my understanding is that the reason is mostly because we needed at least something very quickly and sterilizing vaccines for respiratory virus are harder to research. It is not inherent property of the technology as far as I know.
Sterilizing vaccines for COVID seem to be theoretically possible. "Natural" infection generates stronger immune response on mucus membranes as well as deep inside the body and that provides higher protection against infection. There's no reason why that wouldn't be possible to replicate using a vaccine. But nobody succeeded at making one yet, so we'll have to see if it's practical.
[0]https://www.gatesfoundation.org/our-work/programs/global-dev...
Not all viruses are the same, and neither are all vaccines.
If you believe most virologists the only realistic scenario is that the virus becomes endemic, similar to most flu strains or other human corona viruses (which makes vaccination even more important!).
If you get infected with COVID there are far more options than "Sit around with a thumb up your ass until you have to be hospitalized and put on a ventilator".
https://www.youtube.com/watch?v=QAHi3lX3oGM
Every person spreading the "horse dewormer" nonsense should be charged with manslaughter. The politicization of this whole thing is beyond a fiasco.