Why not at United, If James was signed and given chances with nothing but his speed as his asset, why not Benrahma. As others have stated, Unless James has space to run into, he is easily nullified as the premier league has shown, but a player with technical skills is far harder to mark out of the game.
Also the thing about players from weaker leagues not being up to the standards, I don't go for that. We had Schneiderlin who I thought was absolute class stink it up, yet we signed player a player like Ole from Norway, Schmeichel from Denmark and they served United well for a long time. It depends on the mentality of the player and how they settle. Even as recently as Fred, he signed from Ukraine, looked clueless at the start but is now a useful player as he knuckled down and worked hard.
If the player has an attitude problem, then that's a different matter.