The problem with Pfleger is that if he were disciplined, he would just found his own schismatic church, the way that black priest in D.C. did. Also, what he is doing — while it’s not his job and gives scandal — may not be prosecutable under canon law. (IANA(c)L)
People have similarly asked why he isn’t reassigned to another parish, the way priests are commonly rotated every few years. Simple...he brings in the money, in an area of Chicago where most Catholic churches have either closed or are barely hanging on. Take him and his personality cult away, and St. Sabinas parish is effectively dead within a year.