Tendo

I think a large part of the reason people are complaining about lack of plot progression is because they don't expect Imu to be defeated here, therefore readers view the prolonged back-and-forth against Imu as "wasting time". In comparison readers loved Roof Piece even though that was an extended back-and-forth against Kaido, because people read it with the understanding that this is the battle to defeat Kaido so we're in it for the long haul. If everyone shifts their mentality to view this fight against Imu as the battle where they will defeat Imu, you'll enjoy it the same as Roof Piece.