Google Messages has been around since 2016, and Google has been shutting down their other apps and porting the features over to Google Messages. Google has shown they’re dedicated to RCS, and have not displayed any signs of shutting down Google Messages.
It’s constantly being updated to add features, like actually implementing iMessage reactions. When an iOS user sends a reaction, it converts it to an actual reaction on the Android side. When an Android user sends a reaction to an iOS user, it just says “x liked this message”. Google is doing what they can to make the experience the best.
From your 2012 timeline of iMessage, that’s only 4 years after Apple.