I've worked in a company with both union and non union staff and I believe the union benefited all of us without limiting the company in any meaningfully negative way.
Contrast this with shareholders and C level execs who have immense power and often world it to the detremen of the workers.
That same company was literally bought out and our office was shuttered.
Unionising allowed us to collectively bargain for better severance pay and allowed us to prioritize those of us who had additional family/visa considerations.
The union is (mostly) in place to work on ensuring benefits such as sick leave, parental leave top-ups, overtime limits, etc. They also are there to ensure that management respects the rules when dealing with the workforce.
Also, in Canada you are forced to pay union dues even if you choose not to join the Union, at least partially.
Unions are a way of balancing the power equation between companies and workers. Neither side should be in disadvantage.
If FAANGS were to unionize together the field would be even more imbalanced. For instance, Apple already makes US$ 1.9 million per employee [1] which is 19x its average worker salary [2]. Nothing wrong about that, it's a profitable company, but it doesn't strike me as if they're in a unfavorable position.
[1] https://www.statista.com/statistics/217489/revenue-per-emplo...
Given that capital is overwhelmingly concentrated into a few hands, the job "market" is also a monopolization. You can get a different job but the owners are always the same