The committee needs to think long and hard about which features to propose in each docket and what those features should look like, a lot of discussion needs to take place in order to get each docket formed, then the wider public needs to get its chance to weigh in, and then a voting round needs to be held. That process may need to happen several times for a docket, and there's a bunch of dockets planned before R7RSL will be done.

Think of it this way: if the committee was more cavalier about this we'd have the familiar situation where we start with a great language and then every update worsens it until we end up with an abominable horror show.