How else do we gauge what is successful then?
Reviews positive, people are willing to wait in line for it, people are willing extra to get into the land to ride said ride, brings in more guests then any other attraction before it, more merch is being sold because said attraction is made.
That's just my point, I think if the land was empty I'd say ride failed at being an Anchor but it has changed the entire wait times and crowds level for the park.