This is true due to the outrage of Native American groups and advocates, the reasoning behind not using the chief as the mascot at the University of Illinois is primarily due to racist and perpetuating stereotypes and the University's goal to move forward. While some say that it is disrespectful to have Native Americans as mascots for a variety of teams, others also argue that it is honorable and paying respect to the Native Americans, which makes this topic extremely controversial.
Within the article I found from the New York Times https://www.nytimes.com/2018/02/01/us/native-americans-sports-mascots-illinois.html, they discuss how similarly, many teams (nationally) were changing their uniforms and mascots to appease to current times. Administrator, Lisa Miller stated that "'It's difficult for a University to have a mascot that you can't 100 percent embrace'". Going off of that, much controversy has also sparked in that if the "Fighting Illini" had changed to a new mascot, rather than an orange "I", the issue could have been more moveable and forgotten about by now.