Siebel UX is not up to date. Siebel Open UI introduction in 2012 made it possible for Siebel customers to change Siebel UI's look & feel by modifying CSS and writing small pieces of jQuery code. By doing so, you can make Siebel look in accordance with the corporate brand book and slightly improve how users feel using the system. Still, these changes do not bring Siebel UX to the level users expect from web applications in 2019 when it comes to visual aesthetics and ease of use.