It's not so much a "kneejerk" reaction but a reassessment of the situation with a more thorough lens.
RuneScape has hundreds if not thousands of variables and situations that could come into play in these cases, when reviewing what should and shouldn't work we didn't quite hit the mark with the initial read on the clan avatar buff, it fell into the bucket of "buff players can earn through gameplay" and wasn't given enough scrutiny at the time to catch the concerns people have raised here such as "not enough time to react to its inclusion".
In an ideal scenario this information would have been released sooner, giving all players the time needed to prepare the clan buff regardless of how active they had been prior, but due to combat being arguably the biggest pillar of this skill we wanted to give the team as much time to refine aspects as possible and this has had some knock on affects.
While I agree that revitalizing the Clans system to have more impact is a good thing, I don't think attaching it here without more notice would be a positive.