Good thing Square-Enix doesn't make all its choices based on the opinions of a few embittered internet forumers...

If they actually believed everyone who made a fuss about "omg every game should be like ______" or "omg everyone thinks _____ is crap!", then we'd all be playing 2D remakes of FFI, with no new added features or FMVs, yet somehow made innovative and new without changing the formula at all. No matter what they decide to do, people are going to whine because they don't like it.
Personally, I think it's better that they try new ideas than simply treat us like imbeciles by spewing out identical games with no new ideas.

X-2 is understandably not everyone's kettle of fish. The plot is far more complex than most critics realise, since it takes time and effort to uncover it, due to its fragmented and non-linear nature. The game is basically a coda - an add-on to FFX, so of course it isn't a whole new adventure with a whole new cast and new world. I'm not sure what people expected from a direct sequel to an existent game, but I'd personally have been more disappointed if they'd simply given us "more of the same".

Each of the game's "departures" makes a fair amount of sense, when examined in context:

A fixed party of three playable characters - the previous game was a 'journey' story, with new members acquired along the way. Since X-2 dealt with an alread-established cast, inventing all-new playable characters would've just muddied the story. The way it was done, the majority of the cast were familiar, with a few new additions whose back-stories wove in well with the main flow. Trying to find excuses to bring in a half-dozen new playable characters would've been extremely contrived, and also extremely boring to players who experienced exactly that in FFX.

The "girly" style - with three young women as lead characters, I really don't know what people expected. Not everyone can behave like Solid Snake; the way the X-2 women acted was fitting with their characters. I'd rather have a cast that's believable yet occasionally irritating (e.g. Tidus, Rikku in X-2) than a bunch of perfectly heroic, utterly flawless and absurdly unrealistic constructs.

Starting with the airship - makes sense, really. Most of the world was explored in the previous game, so making the player trudge through every city in order again would've been tiresome in the extreme. "Oh wow! A new city! One that I saw last month while playing FFX - I'm totally excited..."

Non-linear, mission-based story - again, it helps to distinguish the game from its predecessor. It's also a natural side-effect of having an airship available from the very beginning. Approximately three billion nerds have wasted a total of 400,000 years by moaning on the internet about how FFX was too linear, so X-2 may have helped to placate them. Giving the player freedom to do whatever, whenever made the multiple endings possible, and meant action-oriented players could skip dull side-quests while gamers craving a deeper, more thorough experience could take the time to explore everything.