You know Berube didn't have a guy as good as Nylander or Matthews on his 2019 Blues team but he also had Parayko, Pietrangelo, Dunn, and JBo on defence and he made good use of them.
Defense wins championships, can't have half your cap allocated to four forwards, one of which is past his prime and another who's a regular season perimeter player.
Also despite that cap allocation to four forwards, Leafs can't dominate with one line like Landeskog/MacKinnon/Rantanen could.