There's at least two schools of thought here.
The first is that the cherry on the tree defines how good the coffee can get, and that every subsequent step in the supply chain from bean to cup -- picking, sorting, processing, moving & storing, roasting, and drink preparation -- can only mess this up to a greater or lesser extent. George Howell is particularly associated with this theory.
The second is that one can use any set of beans, good or bad, to create a blend with a taste profile that matches, as closely as possible, the Platonic ideal of espresso held by a roaster or cafe owner with exquisite taste. Here the roasting and drink prep become the creative art, and having the right gear and technique becomes much more critical. David Schomer in the US, and the National Institute of Espresso in Italy
, are particularly associated with this theory of espresso.
George Howell's Addis Ketema SO was one of the best espresso's I've ever had; but when it comes to dark chocolate bombs with a hint of berries, Schomer's Dolce is hard to top. So my take is that if you want to taste the full range of great espresso, you'll need to accept ones that are made according to theories that contradict one another; and if you only have espressos that are logically consistent with your favorite theory of good coffee, you'll be missing out on some very good shots.