The Capitol

I'm not convinced that Cardiff is big enough to sustain the current size of the city centre, maybe more residential would be a answer?

I don't think the centre itself is too big (it's very compact in fact), but there is an oversupply of shopping space for the world of 2023. There need to be more reasons to come to the centre which don't require you to spend money. Sounds like the mooted redevelopment of Debenhams recognises this.
We'll have to wait and see whether places like the Canal Quarter become destinations in their own right (like a smaller version of Cheonggyecheon in Seoul https://en.m.wikipedia.org/wiki/Cheonggyecheon ) or whether it will only really be visited by nightlife punters (like Manchester's Canal Street).
As for the Capitol, the basement has hosted lots of pop-up arty events and cinema screenings, while the cinema has been turned into a thrift shop. With a bit of courage, it could be reinvented as an independent business incubator, but it would likely need a lot of grant support. Demolition and redevelopment is probably the best long term bet.

I'm told there's some exciting news coming up for The Capitol very soon, so keep your eyes peeled.

I'm told there's some exciting news coming up for The Capitol very soon, so keep your eyes peeled.

Wrecking ball?

There is a planning application for Capitol to add advertising/wayfinding boards to direct people to the Gravity Leisure Hub that is going to come to The Capitol
Never heard of Gravity before but from their website, looks like they will need a decent amount of space

Gravity Max is a phenomenal signing for The Capitol. They’re an immersive gaming arcade with electric go-karting, mini golf, shuffleboard and VR experiences. Since the opening of the first Gravity Max in 2021, the chain now operate 4 sites in the UK, measuring between 60,000 - 100,000 sq ft. Their site at LandSec owned Southside Wandsworth occupies an old Debenhams unit, whilst their largest site at Liverpool One occupies a proportion of an old Debenhams unit. I fully expected the impending arrival of Gravity Max in Cardiff, however I had them down for the new leisure unit overlooking the upcoming public space at St. David’s. That being said, I’m thrilled they’ve chosen the Capitol. This sizeable signing could really change the fate of this end of town and attract some new tenants at The Capitol centre.

Looking at the planning application, it will be taking up the majority of the centre, the internal entrance is well into the main arcade and it takes all the space from Station Terrace to a few units beyond the first Queen Street entrance.

Hopefully there are some external improvements planned as it's a mish mash of not very nice design at present, although I expect not judging by the elevations on the planning app.

https://www.cardiffidoxcloud.wales/publicaccess/applicationDetails.do?activeTab=summary&keyVal=SCX8QFECM2O00