I'm looking forward to the movie. I think it'll help that the first volume has a definitive beginning, middle and end and a strong cohesive storyline. Start at point A, end up at point B. As soon as the second volume started as an ongoing, all that cohesiveness was lost. There was always that sense of making it up as it went along that's been continued since, with arcs instead of one overall arching storyline. In that respect the first volume was pretty unusual anyway. But it made anything that came after less gripping.
Runaways never lost quality under BKV, but it did lose tightness and direction.