I like Jack, both on and off the pitch. I don't think he's the solution to every problem, but I do think he has quite a specific and useful skillset that, when he's on it, is hugely beneficial to us (and to England in the past too). For all that Southgate seems to think of him as a maverick, as others have said he's not that at all - he's actually very selfless in his willingness to be what the system and the match needs.
He's had a shit season. I don't think it's down to any one particular reason. It's more that his season just kept being interrupted, whether by illness or injury or the break-in (I don't care if other people have had more traumatic experiences, it's not a competition - something like that will fuck you up). It's been one thing after another and he's a confidence player - he plays best when he's in his rhythm and feels like he's doing well. So all those interruptions, combined with the form of Doku (who I also really rate) have taken their toll both in terms of his match fitness and the psychological aspect. I thought he showed flashes of the previous season in between those injuries but he just never managed to get going and build up any kind of form.
Personally I'd still have taken him to the Euros, although I can understand why Southgate didn't. His chance creation, his gravity to draw opponents to him, the way he keeps hold of the ball, his defensive contribution...all great for international football. Not to mention his understanding and interplay with Phil.
I do sympathise with Kyle a bit if he was asked about Jack directly. If he stands up for Jack, admits to being shocked, in any way implies it was the wrong decision, then it looks like he's undermining the manager and disparaging players who were chosen instead. Hopefully Jack's got his ears blocked to those kinds of comments and is focusing on rest and spending time with his family before returning to training with City.