It’s just really bland. I wouldn’t refuse a sandwich that had it on, but I also wouldn’t deliberately choose to pay money for it. It might be partly like the sprout thing? The generations older than mine tend to recoil from them because they have childhood memories of bitter, over-cooked balls of soggy mush. Maybe we had too many under-ripe/poorly stored ones and they are actually nicer today?
I don't get why people go mad for it, either.
I have very fond memories of a sandwich shop that sold a turkey lemon seasoned avocado sub called a “turk-ado” when I was a teen. I don’t mind avocado on good bread, but unless you have a tree in your backyard, you’re spending about 10 to 20 times what butter would cost. It’s the money. Even in areas where the avocados have always been good, it’s the money.