This is starting to go a bit off topic from Duel, but it’s an interesting discussion, so I’m going to roll with it.
We’ve certainly seen more dark rides recently than water rides. When was the last time a UK park built a major water ride? We had the Battle Galleons in 2008, so hardly recent, and I don’t really class Battle Galleons as a major ride, at least by Alton Tower’s standards. The year before we had the Viking River Splash at Legoland. That probably did count as a major water ride, but we’re talking 14 years ago. Some of the Lego models on it are impressive, but as a whole package I thought it was very mediocre. The Lost River in 2004 was maybe the last decent water ride built in the UK.
We’ve got other topics lamenting the lack of flat rides and live entertainment. By contrast we’ve had several dark rides at Legoland Windsor, plus Derren Brown’s Ghost Train and various re-themes, including Wallace and Gromit’s Thrill-O-Matic and The Gruffalo.
We haven’t had more dark rides, largely because there haven’t been very many major rides. A lot of UK parks have closed, and those that haven’t have been cutting back on their investment. When they have been investing, it’s been a mixture of accommodation, themed children’s areas, roller coasters and dark rides.