Yeah I agree that most of the union workers in the US are not particularly well off. Unions like NEA and UFCW are massive, business-oriented, and many of their members are dirt poor. I think the issue we run into as leftists is that we just sorta dogmatically look at unions as a good thing (or at least Lenin's century old formulation of them as useful forms of proletarian organization) or we go ultraleft and reject them as colloborators in colonialism and genocide (which isn't to say they aren't) with very little insight into the internal contradictions of a union, how they came to be this way, or what a union even is. The lack of democracy and the outright hostility to workers self organizing within the big unions fucks their members over just as their protectionism or militarism fucks the global proletariat over.

Near where I live for instance there are union members in mills who are frequently ordered to work 24 or more hours in a row and their local has been outright hostile to any sort of strike or activity to fight it. Idk what their contract looks like or how well they're compensated but they've had multiple members killed in car accidents driving home and many more injuries on the job after working for a day straight. These are the "good union mill jobs" everyone's grandparents had.

There are of course union workers in military contractors and such that are directly benefiting from Imperialism or other forms of exploitation, but the reason the big unions suck is because they are one degree from state institutions designed to choke out proletarian revolution and democracy, not because their members are all living rich off the blood of the global south and have democratically decided to keep it that way. White collar non-union workers in email jobs are much more likely to be true labor-aristocrats that produce nothing than a UFCW grocery clerk or an NNU Nurse.