There have always been barriers to entry to be a programmer. For every self-taught coder, from both the pre-CS as a degree days to the modern day bootcamp devs, there several times as many employers who only want graduates from top-league schools or FAANG experience. Credentialism is not being advocated for by employees, but by employers. If anything, a union could be useful to combat restrictive hiring practices.
The tech world has changed a whole lot in the last 10 years. I know many people who got into the industry by merely going to a tech bootcamp, which got them into a junior engineering position.
Yes, there are still barriers to entry. But the barriers to entry have been massively reduced over the last 10 years. Going to a bootcamp, and getting a job within a couple months used to be unheard of.
Your opinions on what a union "could" be are vastly different than the opinions of what other people want. This whole thread is me responding to a person who literally wants to raise the barrier to entry to tech.
Credentialism is very much being advocated for, by many pro-union/pro-guild people. And history has shown that whenever a union, in every single industry in the world, gets enacted, the result is higher barriers to entry.
Go look at the American Medical Association. Go look at the American Bar Association. Go look at the actor's guild. Screen writers guild. Whatever. It doesn't matter. Pick any high skilled labor union/guild and you will see an organization that is creating barriers left and right, and making it harder for people to get into the industry.
Yes, the current tech industry could be better. But the pro-union people are the ones who are most advocating in favor of keeping out competition/newbies/immigrants, you name it.