The major issue I see is the lack of foresight from the park.
It was known that the weather would be cold. Thorpe know that they have these restrictions about rides not being able to open in cold temperatures. Yet they probably had somewhere between 16-18k people come through, knowing that sooner or later a good proportion of major rides would close. And their response on social media boils down to 'Fright Nights is popular, the weather is cold, not our fault, soz m8'.
The park have taken zero responsibility for this. And yes, weather is out of their control, but they can control communication. A forewarning on Thursday/Friday about the weather, giving guests tips on how to make the most of their day, etc, advising people the park will be busy and consider alternative days if possible (the latter of which they did at 2pm yesterday..). The attitude of the park stinks in this situation. Then telling guests 'you couldn't possibly do all Fright Nights attractions in one day, you'll have to come back to experience them all' is a disgrace.
And when they only have 3 indoor mazes (5 indoor attractions if you count Screamplexx 2D and upcharge-Containment), it screws the park up even more. People are told to wait till night time to do those ones as they're scarier, do some coasters in the evening as their quieter, etc. But when it's cold, and the coasters aren't open, indoor attractions are no doubt more preferable over outside ones.
The park were able open the 3 indoor mazes at 12pm yesterday, which shows they at least had some thought go into yesterday - "oh, Saturday will be busy, let's open 3 mazes early to increase the park's overall throughput per hour and give people more chance to go through the mazes". But in some ways, it's worse, because it makes it seem like they thought that would be enough to compensate for everything else that could go wrong.
The kick in the teeth for people will also be how the park said "we are not at capacity". Given the numerous complaints, it's clear the park did not handle the numbers yesterday. Imagine having a terrible day at park, and being told 'sorry, but the park can be even busier than this, so it could be worse'.
On top of a lackluster maze selection, the park have - arguably, once again - screwed up Fright Nights again from a customer service / satisfaction perspective.