1) the notion of design has been subtly replaced with style;
Sleek wins over functional. For instance, scroll bars on desktop UIs were thrown away, because they were too fat for phones, and phone UI now sets the trend. So nobody among designers cared that the scrollbar you see with peripheral vision does help you orient in apps.
2) styles are in perpetual rat race, you must be trendy and throw away anything that's drawn to 5-year-old fashion;
3) constant feature creep; Social network VK offered music playing, but over the last 5-6 years the number of taps it takes to start playing grew from 3 to 6 or 8 if you need a particular playlist. It's just awful and irritating.
Consider public transit apps. In my city, you must do 15-20 taps to see the routes you need. I struggle to do this while walking. And I have a good vision -- imagine how tough it is for an old man. But a public sector manager, who drives a new sleek Mercedes and never took a bus/trolleybus last 20 years, tells you this is the future.
4) imprecision of touchscreens and curvature of a thumb. Feature creep requires to stick more and more items in the screen, and on a phone, you must be able to hit 1*1 mm area with a rather flat surface of your thumb.
I've only driven Renault Logan derivatives that have no touchscreen, and kinda scared of the perspective to have to deal with touchscreen while driving.