It sounds like you stopped reading all those sources as soon as you got a definition you liked and didn't bother scrolling to get a complete picture of the term.

From Collins[1]

>any program or practice of racial discrimination, segregation, etc., specif., such a program or practice that upholds the political or economic domination of one race over another or others

From Merriam-Webster[2]:

>the systemic oppression of a racial group to the social, economic, and political advantage of another

From Wikipedia[3]

>Institutional racism (also known as structural racism, state racism or systemic racism) is racial discrimination by governments, corporations, religions, or educational institutions or other large organizations with the power to influence the lives of many individuals. Stokely Carmichael is credited for coining the phrase institutional racism in the late 1960s. He defined the term as "the collective failure of an organization to provide an appropriate and professional service to people because of their colour, culture or ethnic origin".

Racism isn't purely about the belief that one race is superior to another. A system that oppresses one race in favor of another is racist. This example meets the definitions of all three sources.

[1] - https://www.collinsdictionary.com/us/dictionary/english/raci...

[2] - https://www.merriam-webster.com/dictionary/racism

[3] - https://en.wikipedia.org/wiki/Racism#Institutional