I certainly understand the reaction to it, but I hope people are realizing how messy messages and iMessage are from an anti-completive standpoint.
Right now, even if you leave the platform and turn off iMessage, your group messages don't function and you have to create new ones. If you choose not to use iMessage, you're stuck with a terrible looking green color without any option to change it. You also loose out on many features (send photos in full res (or even a resonable resolution), videos, and do video calls, etc.)
I personally don't like FB Messenger much, but I'm sure there's many out there that prefer it. Same as WhatsApp, Signal, and I even use Telegram for some friends as it's cross-platform (and you can edit messages).
Biggest thing is messages isn't cross platform, and that's really messy and will likely get Apple in trouble at some point.