The theming argument has always confused me with Hyperia, since most traditional hypers (which, let's face it, Hyperia pretty much is, in the sense of it's a chain lift and drop coaster) simply don't have theming.
Hyperia's plaza is simple but does the job. It could be better, yes, but it works.
The landscaping at the moment is, frankly, dire. The lake has barely been refilled (if you look, there is effectively still land which breaks "Hyperia's lake" and the "main lake" up. That shouldn't be the case, and hopefully will be rectified. I'm sure that foliage and such will grow over time (as is the case for many coasters), but that still doesn't mean it doesn't look great currently. But short-term issues for long term gains.
They do need to look at the trim and water effect. It's seemingly been shut off because of the dirt build it causes around there. Either find a solution to stop it getting dirty, suck it up and accept the dirt or re-landscape it and don't bother with a water effect (a tunnel with some lights and audio could work there instead, for example).
All of that aside, Hyperia is still fantastic. It sits in the lower-end of my Top 5%, and for me having a coaster that close that I can - and do - literally just pop down to is incredible. The length and Mack-ness to the ride understandably means it won't rank as high for everybody, and I'm sure other UK coasters will rank higher for some. But it is designed to be short and hard-hitting, and I think it does that pretty damn well.