One of the reasons I've stuck with Barclays is that their banking app and online services are extremely good. I have both Barclays banking, and Barclaycard apps. Whilst the Barclaycard app has less features, the standard banking app manages the Barclaycard account side of things anyway, so I really never have any need to use the Barclaycard app for anything, perhaps the free Experion credit report from time to time, but that's about it.
I was a bit annoyed that Barclays were not adopting Android Pay, but in reality their own contactless payments on Android is more convenient anyway, with more control.
The other major bonus is that calling Barclays via the app directly means you bypass all the usual identification steps at the start of the call, as you're already authenticated through the app. Nice to be greeted by name and have your questions answered right away. It's a small thing, but these things matter.