Why is the healer class basically a one spell dps class?

[SpiralMask]

@OP: previously AST and SCH did have more depth so that they had something to do when healing wasnt required, either via direct dps or party utility; be it damage buffs (damage, crit, weapon/cast speed, etc), alternate buffs such as damage reduction or mana recovery etc, enemy damage debuffs, alternate debuffs such as stun/silence/slow/etc, precast esunas, and more). WHM did not, and this was a major valid complaint from WHM mains since ARR, that especially picked up after AST was introduced in HW and gave it TWO complex counterparts, with their only supposed niche being big chungus heals (and regens--except the ones that SCH and AST also had).

now rather than give WHM something to do during downtime (which i suppose could have been addressed at some point during the... three? complete lily mechanic reworks), they removed such activities from the other two in their entirety and pruned down WHM for good measure.
this was done while completely ignoring the core gameplay designs of SCH (strong OGCD healing suite and shield GCDs so that they can specifically buy adequate time to maintain their many DoTs or micromanage their pet for greatest effect) and AST (constant moment-to-moment decisionmaking regarding their sects and card system, between the buffs themselves and whether to modify them in some way for greater effect, and who would most benefit from them).

a few reasons cited during interviews and LL's were soft 'action limits' relating to how many buttons a mouse+keyboard or controller player should reasonably have to have on-tap at any given time--this does have some merit, as it's also been an issue for several other classes such as NIN's old incredibly strict rotation timings to squeeze all their myriad attacks and buffs in, or ShB SMN and SB BRDs "piano" approach of pressing everything that isnt currently on cooldown, all the time via constant weaving or double-weaving, or SB [dark arts] dark [dark arts] knight's [dark arts] constant [dark arts] OGCD [dark arts] tapping--coincidentally, recent BLU has been playing around with skills that are multiple skills in one, such as skills that toggle into other skills like cold fog/chelonian gate/phantom flurry, or skills that are conditional based on stance, etc, which could provide avenues for other classes like healers to gain more depth without increasing the number of buttons on your hotbar, as well as PVP/npc story sections having auto-combo skills as another option.

another reason being that healers were abandoning healing in lieu of dpsing more; yoshi posed this as a 'healer vs healer' problem during SB when commenting on seeing a WHM+SCH team where the WHM was left to do all the 'heavy lifting' (the class's only strength, and lacking any options to contribute otherwise in comparison) while the SCH spent the majority of the time DPSing and only throwing out shields or OGCD heals when required (which is again the class' strength, using their healing kit to cover any emergencies either preventatively with shields or as-needed with OGCDs while maintaining their DoTs/pet with the bulk of their time--or simply trusting their co-healer)--which was taken as a reason to look into nerfing SCH and AST rather than giving WHM something other than massive healing to put their time towards--or that WHM being powerful enough to effectively solo-heal content isnt already a great strength, or a problem with basic encounter design/overal healing-done expectations.