Haven't they spent the last decade expanding into new markets successfully though? And from what I gather their new customer retention and satisfaction is among the best in the industry.
People like to explain away Apple's success as merely the product of "fanboys" they've had for decades, as though the same 10 million guys who bought the first iphone are somehow responsible for the 50+ million phones apple sells each quarter. The truth is simpler: (1) yes they do have many loyal customers and (2) those customers keep buying Apple products because they have good experiences with them. It's also true that their design priorities are not universal and some are especially ornery for power users. But the idea that their UI design is inherently bad seems off and the fact that people keep copying them [1] seems like the best evidence.
[1] https://www.theverge.com/2018/10/17/17988564/chinese-phone-s... , money quote: "judging by the accuracy and specificity of the rip-offs, the camera app from iOS 7 has a serious claim to being one of the most influential software designs of the past decade."