If they had a proper banking website and didn't expect you to use an "app" on your phone I might be more interested.
The reality is that you never really use the app anyway apart from very occasionally. The "UI" for this bank account is the card itself.
I prefer the traditional physical bank only for security I only do online banking with my secondary bank which I only keep 100 quid in.
Traditional PC security is way too complex for non-technical people to manage effectively, so the approach of walled gardens and vendor managed security is the way to go.
Not to say that a technical person can't achieve a better level of security with a PC/Mac, but for non-technical users, it's going to be mobile all the way.
This alone is probably a decent competitive edge over traditional banks.
I would certainly be more interested if they did have a website. That's the thing that I don't get with these new fintech companies. Most of my banking involves sitting down and looking at a minimum of 2 windows I don't really get how an app only workflow would be tenable for me. I definitely don't understand app only share dealing. Am I expected to check my shares on the morning train? I've tried chip which is part of this fintech wave and is billed as a savings app for loose change, but doesn't pay interest, except via referrals, and the interface is a bot, except it isn't, its just an anthropomorphised menu that makes basic stuff hard, and it has gifs.