The problem is that they came up with a novel (and hopefully better) approach to UI that works wonders on smartphones because it's a greenfield - there is a new, suitable HID (touchscreen) and no legacy or broken interaction models to support in the first place.

Then they tried to port it to desktop, where touch interfaces make no sense whatsoever and still keep a ridiculous amount of backwards compatibility with everything, as usual. The obvious result lacks conceptual integrity and is so full of compromises that it doesn't even make sense.