Being a good player is not a criteria to becoming a good coach. In fact, there's a trend of most average players who turn out to be great managers of their time. The likes of Sir Alex Ferguson, Pep Guardiola, Conte, Arsene Wenger where not really talked about as top players during their professional careers but performed exceptionally well in their managerial careers. Interesting enough, there are players like Thierry Henry, Paul Scholes, Rooney, Gerrard and the likes of Lampard that we are talking about. Seasoned managers like Jose Mourinho never really played professionally as players yet he recorded great milestones during his active years.
So in essence, a good career will not be a guarantee if being a coach can bring success to the team you are managing and in fact that is how it is so far. The great coaches you mentioned have the capacity to win various titles with the brilliant tactics they have and I think we rarely see that today.
Meanwhile, the new young coach who went from being a club legend couldn't even apply his neat system when he became an active player and perhaps this is his individualistic ability that must be questioned. The EPL has always been a place of competition for great coaches and unfortunately we haven't seen that return and maybe Pep Guardiola will still be a coach who has no competitors for a while.