Not a single thing you said is right. Goff certainly hasn't matched the highs of Warner, Manning, and Brady. But those guys are all HOF QBs, and Goff isn't even yet in his prime. His lows are not the average of his play, and he has put together good seasons in the past. In fact, let's talk numbers. Here are the 2017 and 2018 regular seasons COMBINED for two QBs:
QB A
24-8 record
760/1151
66.0%
8932 passing yards
7.8 YPA
61 passing TDs
5.3% TD%
19 Ints
1.7% Int%
100.2 Passer Rating
QB B
24-7 record
660/1038
63.6%
8492 passing yards
8.2 YPA
60 passing TDs
5.8% TD%
19 Ints
1.8% Int%
100.8 Passer Rating
I imagine you want to know whom these two QBs are. QB A is Tom Brady. QB B is Jared Goff. That's right. Goff put up essentially identical numbers to Brady over the totality 2017 and 2018 regular seasons. Cut the kid a break. Let's see how he finishes this year. I think he's going to play quite well down the stretch. He has his inconsistencies, but he's not yet in his prime.