Big part of the solution.
I find all people talking about Morata ability to replicate Zlatan's numbers as if this is our only problem. Morata can score 30 goals next season and we can still finish 5th because his teammates decide to score only 5 goals each in the league.
Whoever we buy this summer we won't change our whole attack. Mikhi, Pogba, Mata, Martial and Rashford all of them need to score more goals, at least +10 for each one of them in the league if we want to win the league.
I'm sure of Morata being able to score +20 next season and his movement will help the team overall and give us much dynamism. The real hope next season is the other players improving their numbers, and I'm expecting a lot from Pogba and Mikhi since they'll be the main creative force in the team and they need to start scoring more goals than last season, since we're also getting a DMF like Matic or Fabinho that'll free Pogba from defensive duties and make him more offensive.