The more I think about it, the more it seems like Naughty Dog were in a no-win situation with any sort of TLOU follow-up.
If they'd done the same basic storyline and game design as the first, just with Joel and Ellie a little older and showing their relationship developing further, people would have been complaining it was a rehash.
If they'd changed up the gameplay to shift away from the survival horror aspects and focused more on Joel (or Ellie) massacring infected by the bucketload, it probably would have ended up being Resident Evil 6 all over again.
If they'd kept the same setting but moved to a completely new lead character - or promoted one of the side characters from the first game to the main character - then people would have complained that they wanted another sequel with Joel and Ellie.
Not saying that there aren't flaws with what they ended up going with, but I don't think there was any way a sequel was going to get the same level of kudos as the first game.