RCS is a pile of garbage for many reasons. On Android, it’s locked behind Google’s proprietary, privacy-invasive Messages app, and there is no API for third-party RCS clients (like with SMS). The encryption is also implemented in that proprietary client, offering no transparency and meaning that it’s probably backdoored. No one should ever trust encryption software if its source code isn’t public. People should use actual private messengers like Signal, with open source applications available for all platforms, as well as all of the features you mentioned. The only thing it obviously lacks is SMS fallback, but it’s really unnecessary, because Wi-Fi or cell data are literally available everywhere nowadays.