you're totally right, let's just never trust any vaccine or medical developments due to anomalous chance of failure. in accordance to this, i pledge to never leave my home until i leave this barren earth.
The vaccine does not completely prevent you from getting infected or from being able to infect others. It drastically reduces the chance, especially of the more dangerous symptoms affecting the lungs, but it doesn't grant complete immunity.
Besides, measures like masks also affect many other diseases; this recent winter they were effective enough to reduce influenza-related deaths by over 95% compared to the year before.
“Drastically reducing the chances” is all you need, because everyone else has also gotten vaccinated and there isn’t a supply of bats dropping fresh virus on you to constantly challenge it.
The COVID vaccines really are so good there’s not much reason to take extra precautions as long as you’ve gotten one. Variants don’t even matter since it’s not the flu.