They took too long to get the heroes doing anything heroic, especially as a team. Julie Benz used her powers in private but was mostly against being a hero, and the kids just used it for their own private lives. Only Jim was the sole crimefighter. What's the point of having a family of superheroes who never team up? It's like having Fantastic Four about a family who go about their own business leading separate lives, and only meeting at meal times. Imagine if the Avengers movie brings all these superheroes together in one movie, and they all have separate storylines like in Heroes?
Audiences are expecting at least some kind of team up if you're going to have several heroes in one story. They can't expect to just develop their characters over a long period and only start teaming them up at the end of the season or the 2nd season, because that's too late and jumping the gun, since there may not even be a 2nd season (which there isn't).