Some things can't be readily corrected by a simple let's vote on it again. But it depends on what is at stake and what the process was and when was the OMA violated.

I have seen entire zoning ordinances nullified, complex subdivisions having to be started over before a planning board, and budgets and salary ordinances all starting over and taking months of new hearings to fix. And in that time frame, things change sometimes. Elections happen for one thing and new people are appointed to governing boards.

A Google Scholar search (Public Meetings Act) of Illinois cases brings up 779 cases that have made it to either the Appellate or Supreme Courts. So more than a few make it to court.

I don't disagree that people try to use the OMAs to make a political hullaballoo when there is no real substance (according to the laws) to the allegations like a gadfly might do.