You’re not quite on base, but it’s a fair question. TL;DR — The mRNA COVID-19 vaccines are significantly *more* effective than vaccines against other viruses.
For example, the annual influenza vaccine was only ~30% effective in 2018-2019.
https://www.cdc.gov/flu/vaccines-work/2018-2019.html
This is normal. Vaccines naturally mutate fast, so there’s an element of whack-a-mole to any vaccine development.
For COVID-19, scientists identified the spike protein early on as the element to target via vaccination because it’s relatively averse to mutations. But it’s not a silver bullet.
There are some vaccines that are extremely effective (i.e. chicken pox) but those are the exception rather than the rule.