Oh man, the failures teach you so much about what to grow later! My first messy pile was full of tough squash vines that never broke down. Next season I planted greens right on top because I learned that pile couldn't handle the hard stuff. It made me match my garden plants to what my compost could actually eat. Now I don't even try to compost avocado pits, I just plan around that limit!
Avocado pits will break down if you smash them first. My pile took a year for whole pits, but crushed ones vanished in a season. @evaf12 is right about limits, but a little prep can change what your compost can handle.