If you want to ponder the design philosophy of healers, start with the design philosophy of combat.

Damage comes in two forms: avoidable and unavoidable. Nominally, healers exist to mitigate incoming damage and restore HP after damage hits.

A party playing well reduces avoidable damage to zero. DPS playing well reduce the amount of time available for damage to go out (mobs and bosses die sooner rather than later). Tanks playing well make it more predictable who receives damage (the tanks) and reduce it (mitigations). In other words, a party playing well works to eliminate the reasons for having the healer role in the first place, a profound sort of anti-synergy that tanks and DPS do not suffer from.

Thus, healers and their kits are designed to accommodate some amount of mistakes and some minimal level of player skill, including that of the healers themselves. To arrive at a different design, you'd necessarily have to recalibrate how damage goes out in combat and recalibrate the minimal skill level required to clear content.