Healers feel like they have fewer buttons because most are redundant or have a very specific niche use-case that isn't applicable in most cases to see general use. The amount of total skills that you actually use as you level up feels less than other roles that actually benefit from gaining more skills and see those skills being used more commonly. This is why those buttons create the feeling of button bloat. They simply have been replaced with better versions but the amount of skills you actively engage on using doesn't feel like it increases as much as other jobs.

The primary thing to note for WHM is that a lot of skills with a priority all have only one focus - [immediate healing], which only further excerbates WHM's problem more than your other healers in particular {Cure I / Cure II/Cure III/Medica all fighting Afflatus Solace / Afflatus Rapture}. This is what causes WHM's functionally different buttons to result in mostly oGCDs.

As a result, my HUD usually just looks at the essentials of what has a cooldown -- and most of that is just oGCDs. In terms of oGCDs, WHM has the least number of functionally distinct healing buttons of all healers since a good chunk is in GCDs -- which is affected by a priority system (Cure I/II/III & Medica a.k.a. [4 buttons] can all be replaced with a Afflatus Solace/Plenary Indulgence + Rapture combo, and that's usually more than enough due to how fast lilies generate). SGE's redundant buttons have been modified with Eukrasia (Diagnosis/Prognosis) so they are streamlined to serve a purpose. Funnily enough, while prognosis and diagnosis would be invalidated with addersgall healing, due to shields having a relatively large cd on barrier healers, Eukrasian Prognosis and Eukrasian Diagnosis can see more general use due to having a secondary effect of shields "increasing total maximum HP" in contrast to WHM's Cure I/II & Medica counterparts and a third use for generating Toxikon in some very niche uses. Since they also share the same hotkey as their non-eukrasian counterparts, ultimately every skill is maximized to be functionally different.

Unfortunately, you won't see much of a need or use for Eukrasian Prognosis and Eukrasian Diagnosis in most casual content either since oGCDs also replace GCD healing and the damage is generally low enough to not need a secondary effect of barriers. Even the third effect of purposely applying Eukrasian barriers is pretty excessive due to how underwhelming the addersting gauge is. That being said though, these skills still do feel different enough due to having a secondary and tertiary purpose that other skills can't really replicate even accounting for a priority system, unlike WHM's 4 GCDs.