Though it won't be easy, things are looking up for the American working class.
My hunch is that union membership decline correlated to the hopelessness over the futility of change workers felt over the decades. There was a "why bother - it's not going to do any good" attitude among workers. And for good reason. Unions acted like the very corporations they were challenging, more concerned with their bottom lines (pensions are invested in the markets) and leadership more willing to compromise than fight for workers. I do think workers are getting tired of empty promises and realize the extent to which their money and efforts have been devalued. The real shift in economy will come when workers cross industry, cross disciplines, march en mass under the umbrella of "the working class."
From my observer's perch, most of the drive (no pun intended) for representation is primarily coming from younger millennials and GenZ. They're done w/everyone's shit and not interested in "just making it work." And frankly a lot of labor leaders have become complacent or think it's still 1996 when it comes to organizng.
The leaders that buck that trend (Fain, AFA's Sara Nelson) lead the unions where workers will gain the most in the next 2-3 years. Hopefully, it knocks a few others out of their stupor (I'm looking at you IAMAW), and they follow suit.