I agree.
I'd add the Ronaldo signing to the fatal mistakes in his final season as well.
It's impossible to be organized out of possession with too many passengers who can't press well, or are just too lazy to do so, like Ronaldo, Pogba, Greenwood, and Rashford.
And you can't become a modern day elite team in possession either with the likes of De Gea, Varane and AWB doing the build-up.
Looking back at the squad we had back then and the positions we finished in Ole's two full seasons, I have to say we overachieved. We had good attacking talent and depth in that department (Rashford, Martial, Cavani, Pogba, Greenwood, Bruno), but otherwise that squad was light years away from competing.