Wine aerators are a great cheat on an inexpensive bottle when you're feeling impatient. Older wines are better for decanting. The rough idea is that an aerator is the equivalent of 30 minutes decanting?
I used to manage a wine store. I did a blind test and the aerator did seem to smooth it out. I use it on everyday wine, and for expensive bottles, I traditionally decant and let time do it’s thing.
Simple experiment that got me aerating: Open bottle, pour a taste. Pour another taste through aerator and side by side them to see if you can tell a difference.