Certified GKH Gardening Expert
Seed planted avocados will not have the same fruit as the one that it came from. Sometimes, they won't even fruit at all! To obtain fruit, the first thing on the checklist is that you have a known fruit producing variety that is grafted to a viable rootstock.
Of course, there are other factors as well. This article will explain in more detail: https://www.gardeningknowhow.com/edible/fruits/avocado/avocado-tree-with-no-fruit.htm