I'm not arguing for or against, just pointing out that justifying it has nothing to do with it.
It's not a case of "cheap = realism" it's just that the two have become in ways synonymous with British media. It's only made questionable by the existence of American media... Which is over the top, extravagant and... Well, unbelievable. And that is criticised by the rest of the world quite often. Wrongly or rightly. I'm kind of in favour of a variety, and I like that Merlin do things differently, but I think the immersive, ridiculous, all out magic of show that you're in favour of has it's place too.
In some examples, I has made it acceptable to be cheap... Low budgets have a reputation for provoking more creativity, but increasingly people pass bullsh!t off as being clever, and people lap it up in the film, art, theatre and other industries.
Thing is, Merlin really are not working with low budgets. But they are working with a budget that if they took the "Disney route", they'd end up with something poor. By going the route they do, they end up with something of quality within a different style. Whether or not they should be pumping more money into the projects, since they clearly could, is another thing entirely - as that depends on whether it's worth it for the audiences they entertain.
It's common to associate investment of time, skill and money with good results and to look down upon the alternative. It's why more people "get" representational art than abstract art. It's why Madame Tussauds works. It's why Disney is so good. It's admiration of fakery, of the skill in representation. But it misses some vital points such as ; What is the point? Is it worth it? Do I actually like it? Is it believable?
I'm pretty much in agreement when it comes to things like the fences, which are too everyday. So instead of recognising them as a symbol for the creative intentions, we just see their practical intention. It's the reason I hate Saw's queueline. The use of found objects really does look like the park is just using the area as a dumping ground, because they DO dump similar objects in "behind the scenes" areas of the park that you occasionally get a glimpse of.
But in other areas it works wonderfully. The objects around Nemesis, for example... The campsite under the front of the station with pots and pans and such. The obscure objects on the stall turn. The van. Another example is inside Saw's station, which is not filled with objects identical to those found in the film, (which is what Disney would do) but found objects believably similar to what is in the film. Hex's queue is filled with found objects, too. And, as we've seen from the plane and other vehicles, so will Swarm. If Merlin could have found a derelict church and brought it to the site rather than purpose build one, they probably would have, because it's the concept that matters more than the craftmanship with them. Typically British. And it's really only criticised because in the bubble that is theme parks, Disney is the example of theming. Once you look at the bigger picture, actually it's just normal.
Whether it's a good thing or not? Well, that's just personal taste.
Whether it's successful or not? I'm interested in that too, and I don't have an answer. If Merlin put Disney-like budgets into their projects, would they get a bigger return? If Disney took away their attention to detail, would they get smaller returns? I think, honestly, the answer is... Yes, but it's not big enough yes to warrant the difference in price range. I don't think, anyway. What makes Disney sell is the brand, fundamentally. If Merlin pumped huge budgets into their projects, maybe they'd get people staying on park and thus spending slightly longer? (Actually. I doubt that, on the basis of us Brits are very much "get every penny worth") Maybe the returning guests would be slightly higher? But it would NOT be worth the added investment, especially because the British audience just isn't receptive, anyway.