Okay, there are 3 separate issues here and it will do us all some good if we stop conflating them.
1. Is a question of Jack's performed well in an individual game. Analysis and or even criticism of his performance in a game should be taken as just that. An analysis of his performance in "X" game.
2. Is the question of whether he makes us better or whether he is worth 100 million. This is a different and separate issue and shouldn't be conflated with the first. And to this issue, retorts of "some will never learn and are too quick to write a new player off" are appropriate.
But For the record, I've seen very few comments that makes an issue of this... Thus, I find the retort that claim other fans will never learn to often be a bit disingenuous. Most fans, including this criticizing his performances have not written him off. Period!
3. Whether he cost us getting a stud striker. Now this issue can be summarily answered... NO! He didn't.
Now back to the analysis. He did not not do a good job aiding our press. Almost worse than Aguero at Aguero's worst. That's would not work.
Either he improves or he drops onto the middle 3. You simply cannot be a non-presser in the front 3. Sorry! Love Grealish. Think he is mustard on the ball. But failing to press consistently is a No No. Lest anyone forgets, Mahrez too is mustard on the ball. But he is not the presser Gabby is, and thus he is unlikely to start ahead of Gabby in a big game.
One option is to switch bhim and Bernado. But that would be disrespectful and might weaken us. Soooooooo.... Get better Jack! We need your genius on the field. But you gotta press. It's useless playing any other way.