I wasn't say they were good.
Just pointing out that total yard passing is the dumbest stat you can use to judge a QBs performance. The correlation between passing yards and wins in the NFL is extremely weak.
It's weak in comparison to other stats if you are talking about linear progression of stat improvement-to-win improvement.
But there's also a minimum threshold of acceptability.
I've heard numerous times of how "winners" and "leaders" at QB can be unconventional as passers because they "just have it," or because they have some other skill that makes up for their passing deficiency. Tim Tebow was a classic example, Colin Kaepernick was a classic example, and now Dak, to a lesser extent, is kinda drifting that way.
He's not gonna go 1-11 like Kaepernick, cause he's better than that, but his run of sub-200 yard passing days remains an indictable flaw. Yeah, he can win games like last night and put together an "exceptional" (read: competent) drive at the right time to seal a game, but then he's gonna go out the next week and lay an 8 point stinker at Carolina. In today's league, overcoming two quarters of basically no substantial passing yardage with intangibles and QB options cannot be a winning formula.
But the guys who do not rely on such gimmicks are the guys who succeed passing the ball in the air all day long. Those are the guys who are the consistent winners and playoff performers. Tom Brady, Drew Brees, Ben Roethlisberger, Aaron Rodgers, etc. Who are the guys who struggle passing the ball? Tyrod Taylor, Alex Smith (who aside from last year was a sub-230 ypg QB), etc.
That's not to say you literally can't have success -- Blake Bortles is a QB whose defense and running game is carrying him to success -- but even he is at 241 ypg for his career.
If you want to project a "successful" NFL career for Prescott, Cam Newton is actually pretty much the only QB around who is thought of as a top 10 or so QB with such low averages, but even he is at 230 ypg.
Prescott is floundering at 207 last year and 165 this year.
Not cutting it.
You can talk about rating all you want, but these types of stats mean, necessarily, that the offense is not moving the ball on par with other NFL offenses, and it's gonna cost you games, plural. You can't have playoff success or even really sustained regular season success with a passing attack this anemic.