This has ALWAYS been the case honestly. But, it has outright gotten worse and worse.
Even back in the day, Weapon elemental damage, was far stronger then melee physical, etc. Auras obviously, ALSO all give added, or damaged gained as element. Heralds..
A physical build then used hatred, and/or ash.. which, then is gaining so much elemental, you absolutely wanted to convert your base phys as well.
Frostblades, and ranger cold conversion added to the game...
Much more elem pen added to the game.
Much more % of phys gained as element added to the game.
Flat Added elemental on weapons is kindof shit. As noted, physical conversion with hatred/ash and other sources of "% of phys gained" generally greatly surpasses the power of added elemental damage on weapons. Crit, crit multi, attack speed all more ideal, with that high base phys.
And of course actually dealing physical damage is shit, due to elem pen, and all that elem scaling.
Poison/chaos nerfs also notable in there.
Phys damage needs to be made great for once..