I disagree - Dynamics is frequently purchased in part because of the UI and if you set up security policies and use elements like role centres the actions and structures are simple to use. Most customers I go back to post live are more than happy with the UI. For me to get this pre-live it takes an investment in time and training.
To some extent you are right users definitely want a very easy UI means every functionality in a single form . I have seen SAP and Oracle and there UI is much complex. For some things which users complains in AX can be just training issues which users learn doing things repeatedly . AX does much better in this area.
I think the users which you are talking about are not very much familiar with Microsoft technologies. For example: MS-Office.
AX2012 is popular in the market mainly due to its innovative product engineering techniques: Powerful, Agile and Simple.
There will be always add-ons/plug-ins to support more than what system does and the advancements are proportional to the investments the client is willing to make. Here are few: http://www.microsoftdynamicsforums.com/addons/