Really feel we've hindered his development. There have been times when he's let himself down. But there have also been times where we should have treated him like the special talent he is but didn't. Under Van Gaal he was immense. But under Jose, I always felt like he has lesser room for error than most, and tends to perform inspite of his manager's support rather than due to his manager's support. Last season he was excellent despite Mourinho's lack of faith in him till Sanchez came, took the position he earned and then turned completely to shit and wanted to leave.
All in all, I rate Martial very highly. I think he's better defensively than people give him credit for. I think he's the most naturally gifted attacker we have, and we're making the wrong decision if that left hand side isn't his. Think of everyone we've had who could have played there since martial joined - Rashford, Mkhitarian, Sanchez, Lingard (?) and Memphis. Martial is better than them all and I personally have never seen why any of them is first choice over him, and believe that if the manager saw that too (like LVG did oddly enough), then we'd have a much better player on our hands right now.