DIABLO(I,II,III)

The foundation here is, of course, uniques and runewords, but sets also have their place. It's just that often it's worth using not a full set (for example, for a Venomancer from Tristram, you only need 100% gloves and optionally a belt + shield), or, conversely, a full low-level set for quickly leveling characters (the same Sigon for each starting character, although it's difficult to assemble due to the strength requirement, or Xarus and Angelic...). It simply doesn't leave room for extra repairs on Normal difficulty and speeds up leveling. And for a full set, you need to specifically focus on leveling, and already have it 100%, rather than hoping for a drop (a full Tal Rasha set for a Summoner is a different story than a unique + runeword Summoner). And in general, all leveling builds are divided into builds that require specific gear and builds that can be done with minimal gear (for example, an extremely expensive Hammerdin with zero in all stats except life needs not only the final version of the equipment but also all the intermediate items).
And looking at and comparing the relevance of items based on mods (even in single-player) is completely different than in Battle.net.