The only case I've seen that can be tricky to keep performant at the moment is when you're doing CPU heavy tasks whilst listing out uncompressed images >2mb. Memory consumption of images this size do seem to be a tricky problem, though libs like react-native-fast-image aim to solve this sort of thing.
I'd say almost certainly they were developed badly, there's no reason now why you couldn't make apps indistinguishable from native. My top tip for this is to move away from JS based navigation libraries (e.g. react-navigation), that's where you see a lot of the performance gains.
Performance wise the Patient View app I made shows this off, I sync and encrypt thousands of records and chart them out whilst keeping everything 60fps.
I see, thanks for the answer and cheers for the 100 apps, that's a hell of a pace :)
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