Are you seriously implying Gran Turismo isn't about what Kazunori Yamauchi thinks is a good car game?
Oh, wait. Now I remember. In the US, Gran Turismo 4 Prologue shipped without the "Making Of / Driving Course" DVD that was included in the European version. The one where Yamauchi threw around ideas that have little to do with racing enthusiastically and you where encouraged to drive like someone who's heading to the newsstand to pick up the newspaper.
Gran Turismo's not a racing game, and you should really stop thinking Polyphony ever cared about "the fanbase" (which for the most part seems to still like GT - keep in mind that the GTP userbase isn't even remotely representative). Gran Turismo's like an old friend - when you can't put up anymore with its antics you can tell him to sod off, until then you'll probably keep hanging out with him even tho sometimes he's weird or inopportune (like when they added the Kubelwagen, SS color scheme included).
As far as bugs and glitches are concerned, Gran Turismo may have a lot, but compared to any other blockbuster title that came out in the same period it's a gift from the heavens. Try to play Battlefield 4 online and then come back to me and say that Gran Turismo is a glitch-ridden mess.