Ainge likes players who grind. Smart, Rozier, Morris, Brown, Baynes, Semi, Tatum and yes, Horford - the Celtics have a roster full of these guys and this year there's (still, despite the injuries) enough offensive skill among that group to win in the playoffs. Throughout the season, they play hard and work on defense more often and more consistently than most teamS.
They had plenty of grinders in the past but not enough offensive talent.
I do think many here are selling Philly a little short. This is their first time in this type of environment and if they play their cards right (no guarantee btw) they'll learn from this and shore up their roster to get the right supporting cast. They are a product of media hype - but they've got lots of talent and should be very good moving forward.
They still need to figure out how to win against good teams and in this league it takes time. I think their coach is on a bit of a learning curve too. It wasn't long ago he was coaching one of the least talented teams in the NBA.