Compared with graphite/etc, it absolutely is true. A project is judged against its competition. The things you are talking about (UI, scaling, graphs, etc) are not my concerns with it. I don't doubt that it is "very good", for at least several values of "good", but that is missing the point.

Right off the bat, here are differences between barrier to entry (ignoring the "enterprise" stench and consulting/contracting emphasis for the moment):

  Installation:
    Graphite:
      Homepage -> links to  pip / github / launchpad
    Zabbix:    
      Homepage -> Downloads -> Download -> RHEL binaries?!?!  -> Oh nevermind, sourceforge link.....

  Sending metrics to the system:
    Graphite:
      Homepage -> documentation -> getting your data into graphite
    Zabbix:
      I'll be honest, I just gave up.

It just gets worse from there. I don't want to become my companies "Zabbix guy". I want something that I can just get working as rapidly as possible with as little heartache as possible. Particularly heartache that seems suspiciously intentional considering the number of ways you can find yourself on a "hire us to train you!" page on their site...

Zabbix reminds me of all the things I hate about working for a PHB who makes technical decisions at large corporations. Maybe that is an unfair take-away, but that take-away is entirely their own fault.