The moment developers have a cause they can agree on, they will start to vote for unions. And no it isn't too late at that point, rather it is too early to vote for a union unless you have a cause you collectively care about.
Yes, this is how democracy works in general. You don't get everything (or necessarily anything) you want
Personally the only thing that would really make me quit is if they tried to make me go hybrid or back to the office in any way. My workplace is small (10 engineers) and so unionizing based on that could be pretty easy, but it would be easier for me to quit and find a new job that does do remote
You are misinformed on the law. Free riders can't be compelled to pay dues.
California, Washington and New York are forced union states, most developers don't work in right to work states.