Have you ever stopped to think about the situations? I don't consider it a huge accomplishment that Todd Haley was able to coax Kurt Warner to Larry Fitzgerald and Anquan Boldin, and Ben Roethlisberger to Antonio Brown, into 10 TD seasons. Likewise for Scott Linehan- having guys like Randy Moss, Torry Holt, Calvin Johnson, and Dez Bryant makes things a tad easier. Meanwhile, you hold it against Shanahan that he couldn't get Rex Grossman to connect for 10 TDs to Jabar Gaffney? It shouldn't be surprising that Brian Hoyer to Andrew Hawkins didn't result in double digit scores either.
That's why context matters. The only WR Shanny has had before this year that is remotely comparable is Andre Johnson. No, he didn't hit your magical 10 TD number with Matt Schaub and Sage Rosenfels throwing to him, but I already pointed out that he did produce his two best fantasy seasons, averaged 3.5 more TDs per season, and had a much higher percentage of targets, receptions, and TDs in the red zone under Shanny than he had under all of the other OCs he's played for. Julio probably won't hit your magical 10 TD either this year, and I'm sure if he doesn't score today you'll blame Shanny instead of the all-pro covering him or his QB being 28th in passer rating in the red zone this season. The reality is that he's being targeted in the red zone more than ever in his career, and more than your gold standard OCs are targeting their #1 guys this season.
Your narrative that Shanny abandons his #1 WRs in the red zone is patently false, always has been.