I hate to be a party pooper, but I really can't see how the subreddits doing things like that are in any way a protest.
I highly doubt Reddit cares what anyone is posting pictures of as long as they are legal, and the engagement is high. The only way to post them is to engage with Reddit, whether on their website, through the official app, or through a third party app that has to pay Reddit money to use the API. That's exactly what Reddit wants.
And as for the mods: in a real life scenario, I can see how the threat of being replaced is scary because it means losing your income... but here? They were doing free labour, and as soon as Reddit threatened to take away their power over a corner of the internet, they immediately gave in and proceeded to encourage their audience to "protest" by engaging with Reddit.
I think it would have been several times more effective if the mods just all quit, and everyone who is "protesting" by engaging with Reddit in one form or another (posting, commenting, or just looking and upvoting) just left. I really doubt Reddit is even worried about what is happening now.