For me, pre-shows are totally fine when they're short, to-the-point and/or provide an entertaining experience. Some great examples being Haunted Mansion, Tower of Terror and GotG: Mission Breakout!/Monsters After Dark, Tron. For the most part, I'm not gonna' have an issue with a single pre-show as most of them follow the K.I.S.S. method.
Where things get tricky is when a ride has multiple pre-shows, for it can really fall into the issue of taking too long to get to the ride itself. Now there are some rides which pull this off, Monsters Unchained is a fantastic example as it's two pre-shows feel like they move briskly while also still doing some neat things and staying to the point. And then we have RotR which has multiple pre-shows, but it incorporates them into an overall experience which works nicely in that regard.
But then we have the rides which have multiple pre-shows which feel way too long, redundant and feel like a waste of time to get on the ride. Escape from Gringotts is on the lower end of this spectrum for me, as
@Clive said, if they cut out the antechamber wait between the office and elevators, that would make things better. But then we have Flight of Passage where the second pre-show is fine, but the first is just an awkward drag.
And then we've got Cosmic Rewind which gives pre-shows a bad rep, it really does everything wrong here. A coaster does not need two pre-shows, both of them feel way too long, they're not that entertaining, and I feel the reason they have two of them is all because of the transporter effect which due to its design and execution, it ends of being a whiff of an effect. It all comes together into something I wish I could skip completely, and for me that's an utter failure of a pre-show.