Once you apply facts to your statement, you see it is wrong, isn't it?
The Cowboys were bad when they got Aikman. The Saints were bad when they got Brees (FA). The Browns were bad when they got Baker. The Giants picked 7th to get Eli (traded up with Chargers after SD picked him) and won 2 SBs. The Chargers were bad when they got Rivers. The Colts were bad when they got Luck and Manning. The Rams were bad when they picked Goff, the Bills were bad when they got Allen, the Bears were bad when they got Trubisky, the Cardinals were bad when they got Kyler...The Chiefs traded way up to get Mahomes.
I hate to humiliate you, but this was a nonsensical statement. Extremely so, and so easy to disprove.
Not all rookie QBs develop. Some are out of the league in a year or two.