First off, under Mourinho we've signed:
Alexis Sanchez, Paul Pogba, Henrikh Mkhitaryan, Romelu Lukaku, Nemanja Matic, Eric Bailly & Victor Lindelöf.
The 3 first being technically great players and the last was supposed to be great for a player in his position.
The rumour-mill is ran by journalists who know feck all, but even then Willian is one technically gifted player we're linked with.
He is a hard-working player but that doesn't mean he isn't technically great.
Alderweireld is another who we're linked with who is technically great for his position.
We do have quite a few technically great players who need a better platform to play on (both in terms of defense and midfield quality & tactically), so signing players in other positions who aren't technically great can improve upon those who should be doing the job currently.
SMS as a signing could free up Pogba more, Alex Sandro could free up Sanchez or whoever plays on the left, good CB's can push our play higher or just push the ball faster through the midfield line. It's not all about signing attacking-talent to make a team more attacking.
Just let the rumour-mill go and don't put too much stock into it.