Do you deny that this Celtics team has exhibited those problematic traits?
I don't deny it because every team has exhibited those problematic traits. My contention is that it's not a problem specific to the Celtics. The Sixers just lost to the Hawks. The Raptors just lost to the Hornets. Are you telling me that there aren't fans similar to you on those forums saying "Man this team can't even beat the Hornets, how can they possible win vs X?" It's just really narrow thinking, no offense. The big picture is simple: The Celtics have a better roster and coach than the Pacers based on data and an overwhelming majority of opinion outside of Indiana. If you simulate 1 million games between these two teams, the Celtics should win more than 50% of the games. If you're going to have an opinion outside of this, you're not playing the odds and just want to be a contrarian or skeptic. There's room for people like you in life because you keep people honest, but you're just not going to win a lot of bets in the long run.
Even if you are right and the Pacers win, that's just results based thinking and confirmation bias:
If I tell you to pick a number from 1-10, but it's more likely that the number is above 5, and you pick 3 and win, you might feel like you outsmarted me, but in reality, you just took a bad bet and got lucky. Over a million instances, you'd be worse off.