I agree. I just don't think the odds are in our favor that this will confer lifelong immunity. 3 years isn't long enough especially if we end up with several strains that immunity doesn't cross over.
What you're missing IMO is that you don't need "immunity". You need the improved ability to fight a recurrence, which you would have far beyond 3 years should you get Covid and beat it. And yes, getting the flu one year does make it better the next year if you catch the flu, even a different strain.
Are you scared of a world where every few years you get Covid like the flu and it knocks you down for a week but you know you aren't going to die? Because you shouldn't be.
Again, expecting this thing to come every year or every few years and initiate a new and improved chance of killing you after you've beaten it once is expecting it to behave unlike any virus in the history of mankind. It's just fear porn.