>>...which was very ineffective by comparison.
It's more a matter of the Covid virus being able to change. A vaccination (or actual infection) primes the adaptive immune system to recognize that virus - but if that virus is changed enough that the immune system doesn't regognize it then we're almost back to square one. 'Almost' because the adaptive system is a bit faster with modified viruses as they aren't *entirely* changed.
There are people who have gotten Covid four or five (maybe more) times. The vaccine is still less risky than getting the actual disease - and when you add in the risk of 'long Covid', which goes up with each infection it's even more of a 'no brainer'.