Personally, I didn't think Planet of the Monsters was all that bad. Yes I was disappointed in it, and think they could've done a lot better, but I'm hopeful for the sequel to be an improvement.
I still would've preferred either an anime movie series, or even an anime TV series in the same league as the showa or the hesei series. A continuation would've been really cool. But I think no one outside the fanbase would've watched something like that. Planet of the Monsters is probably aimed at today's video game generation more than anyone else.