I started using Ubuntu when it gained popularity before Unity, MIR, and even the Ubuntu Software Center. There was just Synaptic and the apt stuff, and GNOME 2.
It was an updated version of Debian with Wubi, Ubiquity, and polish that made things "just work". This made it catch on fire, and become a good place for newbs and casual users. And from Debian it inherited a huge amount of compatibility, stability, and familiarity with experienced users.
Ubuntu has had to figure...