Based on your own logic, if 30 out of 32 sucks, then top 10 guys should be yearly studs.
2017 - Keenum - 2nd; Alex Smith - 8th;
2018 - Trubisky - 3rd; Winston - 8th
Those guys sure are world beaters right now (apologies to Alex Smith and his robotic leg).
Goff went to a Super Bowl and is currently 25th, he must suck too. Carson Wentz was 26th in his rookie season (which Josh just barely got out of in terms of games played), he must be trash.
While I'll agree that Josh has his problems and there's plenty of work to do - you can't rest solely on one stat. One season and one stat does not determine whether a QB will be successful or not; especially considering Allen was always considered to be a project. I don't recall anyone ever saying "this kid is a year 1 starter, pro-ready". Instead, I recall hearing, "has all the physical tools, is super raw, needs to sit and learn (which he never got the opportunity to do) and he could, potentially be a top guy."
18 starts in, we're 5-2, we lost one game where we got our asses kicked as a whole, and now the multi-year project QB is now an immediate bust.