Not really the same thing in my view. Most stores are open year round, and are not seasonal. Alton Towers is a seasonal attraction, and is only open according to an opening schedule which is published each year. The opening dates for the season are not known until the opening times are published.
It makes business sense to shut on quiet days, and it certainly doesn't affect their business during busier times of the year. Additionally, most of Merlin's southern theme parks have successfully operated midweek closures without any major backlash in the past.
I am glad see see Alton Towers saving money on these wasteful days, where they make a large loss on operating the park. At a time when things at the park are difficult, this is a good and sensible decision. When the park was prosperous is was OK to open on quiet days, as the cost of doing so was easily absorbed. I would much rather see midweek closures than further cuts at the park.
I am not denying that a few people might turn up and be disappointed, but Alton Towers are well within their rights to set their own opening schedule, and to not open on days which do not economically make sense. I don't understand why some here are so desperate to get behind Alton Towers opening on days which are going to lose the park money, which is desperately needed elsewhere.