@Northwest the rubbery ones are fast cured using sodium hydroxide ( aka lye ) to take away the excessive bitterness.
The best Mediterranean ones use salt and it takes days to weeks to cure them to a correct fitness and palatable taste.
Generally those that have highly sensitive taste function in the bitter ranges don't like olives and some even have allergic reactions when eating them.
I know this fact because I can't eat them and many other bitter foods.
Olives are delicious! I prefer green varieties to black, but I'll eat any. I like just taking the jar of pimento stuffed olives and eating a few by themselves.