Fans/Critics aren't 'blaming' Rondo so much as they are...
1) Questioning whether Rondo is the right PG to lead this season's Celtics squad...
2) Questioning whether Rondo has the attributes and characteristics of a leader (incl. consistency) to lead the Celtics into the next era (post-Big-3)...
Since the team is 'probably' not going to win the title this season, the answer to question #2 becomes that much more important.
On his best days, when he's focused and energized, the answer to both is Yes. During his inconsistent streaks, of which there are many, the answer to both is No. Due to Rondo's inconsistency, Ainge (and fans) has to consider the fact that the answer to both questions is No.
With every other player on this team (at least the top-6 guys), you know pretty much what you're getting night-in, night-out; taking into account that all players have off nights. With Rondo, it's almost a nightly crap shoot.
To be fair and honest, the Celtics don't need Rondo to score 30+ points in order to win, so let's not blow his current scoring prowess out of proportion. On offense, Rondo needs to be focused as a distributor and an attacker, and confident to take the open shot when he has it, but he doesn't need to take 25+ shots per game (he's not MJ and we're not the 90s Bulls).
Watching the Detroit game last night, I could tell that the longer the team went with Rondo scoring and Allen and Pierce not being involved, the higher the chance the team would lose. And, in the end, Rondo stopped attacking the basket, stopped hitting his open jump shots, and Allen and Pierce were cold-as-ice from a night of combining to take 16 shots. There is no reason Rondo should take 27 shots and Allen and Pierce should combine for 16, double-teams or no. This is not Rondo's fault at all. This lies on Doc. He should have tweaked the game plan as the game progressed.
It was nice to see Rondo hitting jump shots, but until he can do that consistently (and that means for more than a handful of games), let's not blow anything out of proportion.
When the team loses, the team is to blame. When the team wins, the team is the reason. Every fan knows this.