The "leitmotif" has been misunderstood. Debussy, making fun of the composer whose influence on his own work he couldn't resist and therefore resented, caricatured leitmotifs as "calling cards" presented whenever characters appeared. That's not what they are. Tchaikovsky, who didn't appear to like the music of many of his contemporaries, complained that Wagner had subordinated his genius to a mechanical system. That's not what he did.
Wagner didn't like the term "leitmotif," was annoyed with the attempts to give them simplistic names, and referred to his themes as Grundthema, or "basic ideas." Far from gimmickry, the motifs associated with certain characters and situations are not simple identifiers - which would be redundant and unnecessary - but tools of expression, association, and recollection which explain and integrate the dramatic development of the story being told. Through the mutation of the motifs and the musical relationships they bear to one another, Wagner can make the orchestra comment on the action with great subtlety, revealing to us the underlying, unverbalized state of mind of the characters and the meaning of their situations.
The fact that Wagner developed this way of composing to the extent that very nearly the entire score of an opera could be built on a set of striking and meaningful motifs has led people unsympathetic to his works, and fundamentally ignorant of them, to accuse him of mechanical procedures or gimmickry.