I don't think one post calling it underwhelming and one more saying "I can see why you say that" really counts as knocking it - and I also don't think we're forgetting the Grand Canyon. The poster was simply expressing that the PW was a let down to them. Perhaps The Grand Canyon didn't have that same effect.
And speaking of The Grand Canyon, while Disneyland's has some more nicely updated effects, the best use of the Diorama overall goes to Disneyland Paris, where the Grand Canyon is the first thing you pass through after Main Street Station and when you exit you're immediately met with the sweeping vista of Frontierland from along the backside of the Rivers of the Far West. It's a really great moment where the diorama seems to give way to you being transported in reality . . . and if you manage to catch it at sunset there's almost nothing better.
DLP features no dinos along their railroad, however.