I have never tried to hide the fact that I am no great fan of Giuseppe Verdi. Among other things this means that I am less than amused by those who think they are exercising their wit by proclaiming that Verdi’s setting of the text for the requiem mass is his greatest opera. The only extent to which I am willing to grant this proposition is that it implies that the requiem setting seems to attract as many bad performers as most of his operas, particularly the ones based on substandard material like Il Trovatore. However, when Verdi had a good partner, as was almost consistently the case when Arrigo Boito worked on the libretto, his music definitely rises above the clichés that abound in the requiem.
Does that mean that we can lay the many faults of the requiem on the text? Not only would that be unfair to the words of a rite fundamental to a major religion, but also it would overlook the significant contributions of other composers from Wolfgang Amadeus Mozart at one end of the timeline to Benjamin Britten at the other. Furthermore, in the context of that attempt at wit, it is important to recognize that both of these counterexamples are responsible for some of the greatest musical scores in the history of opera.
No, it has nothing to do with the words. I would prefer to advance the unpopular hypothesis that Verdi was fundamentally lazy. (This distinguishes him somewhat from Gioachino Rossini, who never seemed to worry about hiding his “inner laziness.”) When Verdi had someone like Boito to push back whenever he drifted towards taking the easy path through a challenging situation, he could rise to the occasion. We see this not only in Otello but also in the reworking of Simon Boccanegra. Il Trovatore, on the other hand, lacked the benefit of such a work setting.
I am also willing to grant that there are conductors who can make Verdi worthy of serious listening even when he lapses into mediocrity (or worse). In La Traviata the first lapse comes when the full orchestra takes over from the initial statement in high strings; but the Pierre Monteux recording (the only one he made of opera, as I recall) rescues this from sounding like a blatant blooper. Similarly, Arturo Toscanini threw so much into that 1951 NBC broadcast of the requiem from Carnegie Hall that one might almost grant that the music is not so bad after all. I have no idea how he did it, but I suspect that no living conductor does either!