I hear what your saying, except RCS is not ubiquitous, is it? As I understand it, RCS defaults back to regular SMS if one party in the conversation doesn’t have it, but IMO that seems to work against the benefits of RCS and delays adoption. I’m not saying Signal is the answer here and RCS has potential, but it seems like messaging is fractured and to ensure you’re getting RCS like features, a choice does need to be made in terms of which app to use.
Look up EDS Lite