I have no dog in this race.

That being said, I guess it’s that it belongs to Google, is therefore propriety, and they have a less than stellar record with honoring privacy and/or keeping projects going.

Add on that telecoms didn’t want RCS to have encryption, which is why the default standard doesn’t have it, and you have a clusterfuck of privacy concerns, longevity concerns, and licensing concerns.

Then there’s the abused factor: https://www.theverge.com/2022/6/1/23150243/google-rcs-ads-india-spam-verified-business