Here's a bit more detail on the numbers. All courtesy of Hoopdata:
http://www.hoopdata.com/player.aspx?name=Rajon%20RondoThis year Rondo is shooting 43% of his shots at the rim, compared to 48% last year. He is shooting a slightly higher percentage (66% vs. 64%). The percentage of his field goals coming at the rim has not declined much.
The "jump-shooting" piece of his game also shows improvement by at least one measure. He is taking 34% of his shots from 16-23 feet and making 39% of those shots, up from making 30% on many fewer attempts last year. In this range, these are numbers one can live with. (As a point of comparison, Pierce is also shooting 39% on roughly the same number of attempts).
Where we really see a difference is in the short-range area (3-16 feet). Rondo is taking fewer shots (1.5 vs. 2.5) and shooting 33% this year, down from nearly 50% last year.
I'm not saying I know how to put this all together, but it might be a more complicated picture than "he's not being aggressive," because he IS shooting at the rim and scoring quite well there. Nor is it "he's shooting more jumpers and doing that badly" - he is shooting more long jumpers, but he's doing that pretty well.
One thing I'd like to know is where most free throws are drawn. If he was getting calls in that same 3-16 foot range last year but isn't now, then maybe this means he is avoiding contact and only going to the rim when the lane is wide open.