Wagner, in my opinion, was an anomaly. A one-off.
Which is different than being a charlatan.

I had the life-altering experience, getting my applied-music degree at university,
of taking a course on the Life and Music of Richard Wagner,
taught by a musicology master (that's music history)
whose ancestry was immigrant Russian Jews, escaping the pogroms.
But he was born and raised in the Bronx,
with the accent and the bellicose attitude to go with it.

He remarked candidly once,
that he could not happily teach a course
on the Life and Music of Beethoven
because he was too in awe of Beethoven to do the job properly.
But, he said,
with Wagner he had a love-hate fascination,
and he found it deeply satisfying
to work this out by teaching a course on the subject!

Parsifal will never again sound the same,
not after the lecture on the Nazis' Final Solution relative to
the -- shoot, what was it? a spear, or a sword? --
touching the Holy Grail, and purifying the "blood"/contents.

There is actually an impressive panel of experts, figuratively speaking, throughout history,
testifying for the influence -- the constructive influence --
of Wagner's music, regardless of Wagner's person.
They are classical music composers themselves.
And I don't mean the composers of weak character
who were stunned by the force of Wagner's compositions.

I mean composers as disparate as Debussy and Brahms.
Debussy, a force to be reckoned with in his own right,
had to grapple with the Wagnerian influence as he matured.
And while Brahms was famously pitted against Wagner by the critics,
Brahms, with his sense of inferiority, his crippling perfectionism,
and stubborn persistence,
added music scores of Wagner to his library of Bach, and Schubert, and so on,
and studied Wagner's music with diligence and thoughtfulness.

Verdi, finally, is a good example of the resigned ambivalence of
other composers to the presence of Wagner in their midst.
I don't dispute the Verdi quote in earlier post on this thread.

It is also a fact that old Verdi outlived Wagner,
and his letters/journal record his response:
"Sad, sad, sad. Wagner is dead!"

Not to mention, that Rossini acquitted himself so well, in
Wagner's presence, insults or no insults,
that Wagner would later confess
that Rossini was one of the greatest men he had ever met.