I think the "letdown" many people are expressing is that these other extras were really hyped up and expected to be revolutionary, but IMO deleted scenes and bloopers are a routine (even expected) addition to most DVD/Bluray releases.
Routine and expected for most shows made today. TNG however is a show that was made 25 years ago where bonus features and extras were not even contemplated. Heck, the bloopers from season one looked like they were made for those who worked on the show and were never meant for the public to see since it has adult language and very blatent sexual references. When bloopers are made today, the actors know that what's being filmed will most likely be seen by the whole world. Back than, not the case.