Something I see a lot of on this and other pro-labor communities is a variation of “yeah, your boss won't fire you for [protected action], but they'll fire you the next day for no reason at all”, and that isn't actually how at-will works. If you're terminated shortly after a protected action such as a labor board complaint or discussing wages with your coworkers, you can place the legal burden on your boss to prove that your termination wasn't retaliatory.
It's also important to note that you usually don't have to pay for months of legal assistance out of pocket to enforce these rights: the NLRB and DOL will often require that restitution be paid to employees if they investigate an employer and find them in violation, and many lawyers will work on contingency if the potential settlement is big enough — and since it's rare that this happens to only one employee, usually there's plenty of settlement money to be found.