In fact, 91% is an amazingly high number - I don't know if any pre-mRNA vaccine has ever reached that level of effectiveness.
So I return to my original point -- if they're really that effective, why the hubbub?
This is a very dangerous idea and why there is so much confusion and misinformation.
By insisting that 91% is "truly effective" in conversations like this you are not helping.
And the virus rapidly evolved and the vaccines we have became less effective to new strains, as expected. A quick deployment of vaccines would greatly reduce that risk (see: Japan currently having infections in the double digits following a rapid deployment in vaccines and universal masks, leaving little room for new strains to adapt).
The pandemic has been a long chain of some insightful people saying "This bad thing will happen if people don't take X precaution." People say that's a lie--then don't take X precautions. Bad thing happens. People get angry and say they were lied to because bad thing happened when they were told it wouldn't happen (because loads of people took no precautions). Then there's a warning about another bad thing happening, followed by denial.