Perhaps some law firms with deep pockets will take your case. This type of case may take several years to resolve. The attorneys need to earn money somewhere else while the case goes on. Just today, a major retail announces it is settling a class action case in which the plaintiffs allege employees were forced to give up their break times without pay. The case has been going on for over 10 years.
The perception of the community changes over time. The law changes with the community. A few years before, nobody could win against tobacco companies. Then came the case in which the tobacco companies lost billions of dollars. Now, awards against tobacco companies are not all that infrequent.
You know that trailers "are understood to be a part of the movie going experience". Commercials in theaters are "a part of the movie going experience" too. You knew going into the theater that there would be commercials. No one tricked you into the theater on a promise that there would be no commercials.
As for not being paid for watching the commercials, the theaters would argue that getting tickets at a lower cost is payment. Without the commercial revenues, ticket prices would be higher. Moreover, there is no legal requirement that moviegoers be paid for watching commercials.
The theaters are not promising that the main feature is shown at the listed start time.
If enough customers complain, perhaps the theater companies will change their business practice.