Why would slow, large aircraft be able to operate in a theater with massive amounts of uncontested advanced anti-aircraft weaponry present? US doctrine involve

Why would slow, large aircraft be able to operate in a theater with massive amounts of uncontested advanced anti-aircraft weaponry present? US doctrine involves SEAD and immediately obtaining overwhelming air superiority, not being confined to the ground or artillery duels. Look no further than day 1 and 2 of Desert Storm - Ukraine hasn't mounted an operation even remotely resembling the scale or complexity (and can't.)