Also looking at the spot it used to occupy, it's toward the "noisy" side of the park. The north and east borders of BPB are bordering residential areas, which means that side of the park is somewhat limited as to the noise level of attractions there (the south end less so since the Big Blue hotel acts as a sound wall, but I don't think the city would be happy with any attraction taller than the hotel). Anything tall and noisy (that is, anything that makes guests scream, since that sound carries pretty far) would be out of the question there, and the coasters already there are probably given special permits because of their heritage status. But Wild Mouse sat in the centre of the park, far enough away from neighbours that noise would not be an issue. This means that Wild Mouse could potentially be replaced with something tall and scream-worthy, if the park so wished.
As for my opinion on the demolition itself... I'm shocked as well, Wild Mosue was definitely on my to-do list. But I understand that the ride could be more trouble than it was worth at this point. Keeping it operational was probably an expensive affair, and any serious HSE incident would deprive the park of way more money than its continued presence would ever bring in. The Smiler crash hit Alton Towers pretty hard, and BPB would probably take such a hit even harder. The impression I get from reading this thread is that securing the ride (especially clearance and such) would be prohibitively expensive, and possibly require a rebuild that would rob the ride of its character anyway. Keeping it open would be very risky, if allowed at all, rebuilding it would be very costly and change what made it popular in the first place anyway. Considering that risk perspective, plus the cost of keeping the ride open, Wild Mouse was probably just too expensive to keep. It could not even be open for a last goodbye, and it wouldn't do any good to leave it in place, out of operation, when guests arrived in spring. Might as well quietly demolish it in the off-season and then quickly focus on what goes in its place. Too bad about the timing, since with Icon being built across the park, it's not like they could slap a "coming soon..." sticker on a fence around the lot and expect anybody to take it seriously.