What a strange comment. Their "hipster stack" works really, really well. It's the best banking UX available by far, and I've moved all my primary banking to it.
I've been using Monzo for 2 years and I have no complaints. The app is fantastic and they have integrations for international transfers, and business banking that just work.
I’ve been using Monzo for around the same time and have had nothing but good things to say right up until they decided to start pushing their Premium/Plus accounts onto customers via in app ads. With all the rumours of them struggling to become profitable it’s made me consider a move to Starling, who seem to be in a better position in that regard.
I use Starling for my business (Monzo didn't have business accounts at the time). The app is much worse than Monzo. However they do have better export facilities, and you can do transfers via website, so for business I think it is more practical.