I liked Apocalypse a lot; I love a good drop tower, and it was indeed a great one! I admittedly couldn't quite get on board with some of the obscene hype surrounding it, but I did still really like it, it was easily my favourite ride at Drayton, and I'll be sad to see it go.
However, I don't see its removal as a mistake by any means, and that is for a multitude of reasons.
Firstly; as others have said, the ride did seem to be limping to the finish line a tad in recent months. When I last rode in June 2022, only one sit down tower was operating, and the others were all covered in tarpaulin and looked like they hadn't operated in some time. With that in mind, Drayton do seem to have gotten a good operating life out of it, and I wouldn't be at all surprised if the cost to renovate and maintain it was simply too high to be financially viable.
Secondly; Apocalypse may be loved by enthusiasts, but I don't think it really gelled with the park's new direction. The park seems to be heavily pursuing the Chessington/Paultons-style family market over trying to appeal to thrillseekers, and while a bit of light thrill wouldn't necessarily be counterproductive in a family park, I think there's quite a considerable chasm between "light thrill" and "near 200ft drop tower with dark theming and scary seating configurations". For that reason, I don't agree that it is/was the park's headline attraction; it may well have been when it first opened and in the 2000s when DMP were a bit more thrill-focused, but I don't think that's the case now that the park has taken on a considerably more family-friendly image and refocused itself to become more of a family park.
Also, I'd challenge the point that Apocalypse was unique and that whatever replaces it will be "bog standard" by comparison. I'd actually argue that its replacement has the scope to be a far more unique ride than Apocalypse was.
Yes, Apocalypse was admittedly a unique ride when it opened back in 2000, and it will always hold the bragging rights of being the first stand-up drop tower, but Intamin drop towers, even ones with the same unique seating configurations as Apocalypse, are not exactly a rare breed these days. Not in the UK, admittedly, but Intamin drop towers, including stand-up models, are not exactly hard to come by nowadays if you look a little more globally. The sit-down experience of Apocalypse is pretty two-a-penny these days, with a vast number of sit-down Intamin drop towers now existing at parks around the world, and even when you look at Apocalypse's unique seating configurations, I can think of a good few others that operate with these. For instance, Hurakan Condor operates happily at PortAventura with all 3 of Apocalypse's seating configurations on offer (and all 5 towers operating, from what I can tell), Golden Driller also opened fairly recently at Fraispertuis City with all 3 of Apocalypse's seating configrations on offer, and I can think of quite a number of stand-up Intamin drop towers in operation.
By comparison, a new coaster could offer quite a bit of scope for something really good and unique. Admittedly, it likely wouldn't be nearly as intense as Apocalypse, but I'd argue that it could deliver in other ways and suit the modern day park far better. It's arguably easier than ever to build a quality family or family thrill coaster, and it's arguably easier than ever for small to mid tier parks to build a quality coaster, so I have high faith that whatever Drayton builds will be truly brilliant in its own way, and be a really good family or family thrill coaster for the park!
