I agree that the typical American five year old isn’t going to be making comparisons between Paultons Park and Legoland Florida.
From an enthusiast’s perspective, there are quite a few reasons why we don’t have a park like Cedar Point in the UK, ranging from planning issues to the fact that many regional parks in America have a completely different business model to anything that works in the UK. Cedar Point’s calendar is based more heavily around the summer than the UK parks, because the US has an 11 week school holiday compared to less than 7 in the UK. Cedar Point relies heavily on frontline staff living in dormitories in cheap accommodation, something that doesn’t seem to work in the UK.
Logistically something like Cedar Point probably wouldn’t work in the UK. There’s no reason why Merlin can’t match Paultons Park’s quality with Peppa Pig. Maybe they will do, it hasn’t been built yet. There are little bits of ‘quality’ that make Paulton’s area feel special. For example, a lot of the signage is 3D rather than 2D vinyls. Does the average 5 year old consciously notice that? No. But subconsciously people can sense the quality of an attraction. They might not have heard of Paultons Park, but perhaps they’ve been to Dollywood and seen Wildwood Grove. If The Peppa Pig Theme Park is a conspicuously lower standard, they might be disappointed.