I can personally kind of accept review bombing if the tool is available. However, to be really effective it needs to be used when there is some confirmation that current owners are getting a worse product. Feel free to correct me but even if Rocket League ends up being pulled from Stream for new purchases, it'll remain the same for current owners, right? If stuff like witholding / delaying patches to Steam or similair stuff happened I'd be a lot more understanding, but currently we don't even know if anything will change ahead of the eventual Rocket League 2.
Correct. It'll remain supported for all current owners. And anyone who buys the game in the future, given that it doesn't look like it's getting pulled anytime soon.