Mount is a weird one for me. I do think he has talent but I don't think he has the creativity to play in that position in that team. Too often attacking moves seem to pass him by.
Too often for England, if Phil or Jack is on the left, Mount drifts left towards them to get involved in intricate passing triangles that look pretty, but it always breaks down because the area becomes congested with Mount, the LW and the LB all getting in each other's way. It's not a big tactical tweak for him to stay more central and draw the ball into more dangerous areas, but the fact that tweak never seems to happen frustrates me and gives me a poor opinion of his positional sense and Southgate's big picture view of the game.
Every now and then he pops up with a nice pass or goal, or some half-decent tracking back, and in some circles it's heralded as the reason he's in the side. But for me he simply doesn't do enough to have that starting position nailed on as he does. Whoever's playing in that position should be dictating play. If Southgate doesn't trust Phil as the 10 (while I disagree, I do get the point that Phil currently plays more as a winger than anything else) then Maddison should definitely be in the picture, pushing for that place if fit. I don't think he's the answer to all England's problems but he is at least a dynamic and consistent danger.
Of course, Maddison's been out in the cold from the England set-up for years, so I can see the argument against giving him his first cap in years in a knockout round of a major tournament - but that's on Southgate and his team, too. Maddison's been playing well in the PL consistently for ages and it's mad that the national team didn't choose to take a closer look at him by getting him involved in the Nations League matches.