It's a shame how this season has turned out for Barkley. He started off great and for the first 10 or so games looked like he had matured in to the player we hoped he could be. But with the team's poor form, his confidence has gone to pieces and he's been awful for a while now. Having Martinez as his manager certainly won't have helped, instructing him that he doesn't have to track back etc.
The issue Barkley has that most have mentioned is a big mental weakness and fragile confidence. Both him and Stones have gone through criticism in their careers but I get the feeling that Stones can handle it a lot more than Barkley because he has a lot more belief in his own ability the whole time. Stones makes errors and puts in poor performances but I don't think he ever looks scared to be on the pitch and mess up. Barkley on the other hand reverts back to the 18 year old who gives away possession, and looks disappointed in himself when things don't come off.
Barkley has to take responsibility for how he plays when he's out of form though. He has to ignore everything he's been told by Martinez, and his own mind when it comes to grafting for the team. When you're not playing well, you have to get yourself out of that rut by putting in effort for the rest of the team. It keeps your manager happy (except for those like Martinez), and it keeps the fans and your team mates happy. That's why I think so many lose patience with him because he looks like he's jogging round half heartedly, which he often is.
I also think some "fans" just love to do players down to make themselves appear knowledgeable about the game. The ones who always comment on the negatives and never the good things that happen. Evertonians were still having a go at him when he was in great form at the start of the season. He puts in a professional performance where he keeps things simple and retains possession well and people moan at him for not doing anything. Then when he tries things and they don't come off, they slaughter him.
He's at a crucial point in his career now, I reckon it will crush him if he doesn't go to France.