Speaking of Ox: there are certainly late bloomers, but usually there are some signs and at least a foundation of footballing IQ, which in this case seems lacking. Part of the issue is that he is a bit like Theo in that when his confidence is low, he is a complete calamity. At this point, he is a useful squad player at best for us imho.
Re: Gnabry - the situation is a little bit of a grey area for AW, but it does appear that he made some wrong choices with Gnabry in terms of cultivating his talent and protecting his upside - instead, he got loaned to Pulis (OMFG) and was unlucky with injuries and never really got much of a run with AFC.
The bigger issue is going into this year relying on a young Iwobi, Theo, and Ox for a crucial wide role and back-up striker (Theo). We should have loaned or sold Ox, got a WC player to pair with Sanchez (either striker or wing) and let Theo fight for his spot wide or at striker and/or be impact sub. Iwobi should not be nearly as important to us as he is this year, as much as I like him and think he will eventually be a very good player for us.
If you subtract Perez (nice player, but depth at best) and Ox (and frankly Ramsey) and get a top, top attacking talent instead, our attack is impacted massively. And especially with Sanchez pushed up top, puts even more pressure on our wide players to contribute offensively.