David Carr threw 9 TD's to 15 INT's, 162 YPG, with a 62.8 passer rating and an outrageous 76!!!!! sacks taken his first year. Not sure what you're referencing.
I think everyone realizes there are QB's who have success right out of the gate and then flame out, but there are way MORE QB's who suck out of the gate and always suck. If Allen does what Watson did in 2017, NO ONE will say "yeah but RG3 and Vince Young and and and...." He will absolutely given the benefit of the doubt, which is what he would deserve.
And yes, if Allen hits, it all changes and I will have been wrong. But give me Watson's chances of being franchise over Allen's chances today.