UK labels just have no idea how to launch new artists in the streaming era. In the digital download era you could promote a song weeks before it was officially released and get loads of itunes pre-orders to secure a solid debut week. More people also watched tv and listened to radio so traditional promotion was much more effective. That's the reason that the few remaining big names in pop muisc (Adele, Ed Sheeran, Harry Styles) all debuted 10+ years ago.
Most pop acts in the UK mainstream are quite faceless and consequently burn out very quickly. Even Dua was pretty forgettable in her debut era until New Rules was given the single treatment. Also it doesn't help that labels keep churning out these disposable dance collaborations which gets quick little hits but doesn't help to establish artists' brands or identity.
Rap is probably the exception here which is doing pretty well. I guess Central Cee has seen some level of success overseas?
There are a few UK artists who have established themselves somewhat in recent years like Sam Fender and Tom Grennan. Their labels have let them release frequently and allowed them a lot of creative control which has worked out well for them. Raye has also seen some success and once again we can see that was due to creative freedom. Labels need to move away from the manufactured pop star formula and just let artists release the music they want to put out. There's no shortage of talent in the UK, people just need to be given the opportunity to demonstrate what they're capable of.