Sure, you are 100% correct; those are the abuses that can be stopped too. Also, when I got my degree, going through the course work, there was a strong anti-union vibe, they definitely do not look at workers organizing as a positive. So it is not surprising that it is looked at as "popular feeling" or "anti-meritocratic". Of course things change, and where things were once meritocratic, are not anymore precisely for reasons you state, such as the ability to work for free, and often on top of having an expensive education.
Except baseline, a union can help with diversity in the RPG industry, something we have all heard about, and seen a lot for desired change. So beyond fair compensation, and preventing bad practices, organizing can also help with promoting the change we want to see in the RPG industry as a whole.
One of the factors that I think many people overlook is the way in which the economic system of the TTRPG market decreases diversity on the production side (and, likely, the consumption side).
If you assume, as do many people here, that TTRPGs are just a lark, a hobby, and that the creatives that work in this field aren't worth paying "real" money, then you necessarily restrict the labor force. Much like the unpaid intern example above- areas that require some degree of erudition (writing, art in many examples) yet don't pay well often tend to attract people that can afford to not worry as much about the pecuniary benefits.
People, such as a person above, who refuse to accept the minimal piece meal rate because just getting a credit is kind of cool - I mean, it's not their real job.
If you depend on the money, if you have to make rent, if you don't have family to fall back on - you are less likely to take those risks. Which tends to be to the advantage of those who can afford to not worry so much ... which tends to lead to less diversity.