For most people in lower wage jobs, the ability to switch job and vote with their feet is a lot more complicated than it is for tech workers. The balance of power is firmly on the employer side, yes even today with labor shortages. I'm sure you read about those amazon workers being blown up by tornados being denied the ability to go home. "They could have switched jobs!" shouldn't be the default answer.

So yes, pros and cons with unions, but let's not forget where the balance of power is right now.