A complex question. One example of why the ear, unaided, is not best.
1. I set up my rig. I thought the bass sounded great.
2. A longtime poster here recommended measuring to see what the SPL graph was, then adjusting things in various ways. I did that.
3. When I listened again, I had no idea how much better it could be. It was beyond my comprehension. Without measuring, I'd have never gotten there.
Repeat the above scenario for measuring impulse graphs and really focusing the soundstage.
The ear is easily pleased. Measurement offers a way to try things which please the ear even more.
It's a dialectic.