Just some devil's advocate spitballing.
Flacco uttering the "here to help Sam" company line is to be expected right out of the box and especially since he has a history with Joe Douglas. At the same time he still wants to play (believes he's got something left in the tank) and with $3M in incentives, exactly how will his "clipboard-holding / help Sam" hold up over an entire season? Further, he's an immobile big-arm QB whose skill set doesn't exactly align with Darnold's. Lastly, while he's dinged up, he saw Peyton Manning come back from a wrenched neck, and, he's the same crank who made a point of saying his job was not to serve as Drew Lock's mentor. just sayin'..
You make some points, but this situation is completely different than Denver.
In Denver, Flacco was brought in to be the guy in the short term, assuming Lock wasn't ready. And a guy with Flacco's history probably is confident he can hold off a 2nd-round pick.
Here, Flacco was brought in clearly to be a backup, and he's too injured to play right away anyway. I think Flacco views this as a one-year hiatus where he can rehab, rehabilitate some of his reputation, and get on the field if something bad happens to Darnold. If Flacco were healthy right now, it might have caused issues, but I think Flacco should have a better mindset now.