Honestly, this isn't entirely Sega's fault, the dev team basically came out and admitted that AP had a rocky development. This was not a game destined to perform well. Not to mention it really isn't all that great. There's plenty of bugs, it looks dated and pretty much everything but the dialogue system (including the story, IMO) was either bad or just plain unremarkable. It barely got any press, had insane delays and probably went through 3 or 4 different versions of the story or levels. Don't get me wrong, I enjoyed the game, but it was no masterpiece.
I do hate the fact they focus so much on review scores, which is always ridiculous. Weak sales justify not making a sequel, not a handful of opinions.
PS: Sega is awful. They are doomed. Making another game with them is asking to sink with the ship.
PPS: Why do we even need a sequel again? Sequels are way too common in the industry these days.