Avocados will also start to turn color and loose their shininess when ready to pick. A bit of a generalization as will depend on variety. But yes you can always pick one to try out and see if it's really mature.
My sharwil turned that way months ago but was not ready then. I think all fruits have visual cues (besides brix and other stuff) that indicate maturity. Gonna give an exmple for wine grapes. I pick ONLY when the following criteria are met:
1. Brix is between 22-27 depending on preferred style,
2. Proper acid/pH,
3. Seeds, very important. Mature grapes will have medium to dark brown seeds that have a crunch when ground in the teeth,
4. Cluster peduncle or stem - lignifies some or totally.
The same type of visual and sensual human criteria should be developed for avocados IMO.