I'm just as puzzled by the F.O.'s failure to draft a killer at this point of Joe's career.
What you said is probably believable to deluded crazy folk but sane people know there are more things to account for than cherry-picked stats. If what you said about Flacco's inability to develop chemistry with "new" receivers is true then it would also apply to any pass-catcher by default since the mechanics are the same regardless of who the pass is designated to. Unfortunately for you there's plenty of tape that destroys your perception of Joe as he can be frequently seen completing passes to drafted pass-catchers with good technique and reliable hands (Pitta & Rice being prime examples).
Another piece of evidence that destroys your superstition about Flacco's reliance on veterans is tape of him throwing to traded pass-catchers who either frequently sucked at getting open and making contested catches or were washed up by the time they got to Baltimore (Lee Evans, Jacoby Jones, Donte Stallworth).
Thirdly, if the failures of the passing game were Flacco's fault as you suggest why did the receivers fail to find success on other teams? Tell me again, who among this group dominated defenders after leaving Baltimore?
Mark Clayton - First round pick. Funny how his appraised level of talent failed to appear in Baltimore AND St. Louis.
David Reed - lol...Dude got a chance to tear it up with Luck. What happened?
Torrey Smith - Largely still a one-dimensional PI specialist who only seems to be useful on short to intermediate routes when he's pissed off. Even the F.O. noticed his limitations and sent him packing.
Tandon Doss - *scoff*
LaQuan Williams - ....no.
Marlon Brown, Tommy Streeter, I could go on but the point is beyond proven. The F.O.'s selection of drafted/UDFA WRs during the Harbaugh era (minus the past two seasons since it's still too early to tell) have been mediocre at best and often worse. NONE, I repeat, ZERO of Baltimore's drafted/UDFA receivers from 2008 to present have gone to be dominant elsewhere. Point me to an instance where Joe failed with a Fitz, 'Tron, A.J. Green-caliber receiver. I'll wait.