After this firm (but considerate) rebuke, I hereby desist from using the G word to describe Wagner's mature works, especially here.And, please, let's here, here most especially, desist from this Gesamtkunstwerk fiction. Wagner soon abandoned that theoretical construct when he actually got to writing the music for his music-dramas realizing finally that whenever and wherever music is involved it's NEVER on an equal footing with the other arts but ALWAYS emerges dominant.
To the stated topic. Can the separate components of Wagner's mature art (music, drama, poetry) — a synthesis of disparate forms that typically exist independently — be meaningfully judged independently?
Synthesis begs analysis — people will judge components separately because they can. But, that is merely the beginning of a critique — otherwise it's just an "academic" exercise — if the aim is to form a judgement of the work as a whole.
For example, judgements confined to investigating an orchestral part, taken in isolation of an orchestral score, could easily condemn all orchestral forms (symphony, concerto) to musical incoherence. Yet people apparently persist in drawing analogous "conclusions" by investigating libretto and score in isolation — even for opera in its Wagnerian form, where this is least applicable.
In imagination, we can consider a bleak world in which Wagner's fused synthetic works didn't exist, but their isolated components (music, drama, poetry, and also philosophy) did.
Yet, in the unified Wagnerian world of synthetic works, none of this seems paramount.
My mundane point — which is not intended as a contribution to the far more interesting "dominance-of-music" issue — is that Wagner has presented us with an already scrambled egg, and that acknowledgement of this fact is the obvious point-of-departure (and nothing more than that) for any evaluation of the composer's mature works.