You could see all your accounts with an individual brand in one website / app, and doing things like opening new accounts online or applying for credit cards isn't exactly new functionality either. I'm sure Monzo is slicker because it isn't talking to a bunch of COBOL in the backend, but traditional banks aren't behind so that basic functionality is missing.
The issue is that Lloyds Banking Group was basically bifurcated by brand, so that the Lloyds app and website only had your Lloyds current / savings / credit cards etc. whilst the Halifax website and app only had Halifax current / savings / credit cards. They're clearly trying to merge things so you only need one app / website.
I noticed my soon to be closed nearest Lloyds branch gained a "Halifax customers can use this bank." poster in the window, I'm not sure if that's just a reaction to the fact that physical bank branches are getting kinda rare, or if it's really taken them about 17 years to merge the Lloyds and Halifax backend systems to the point where branches are interchangable.