You can think that - but Venom just isn't a good movie. When the main positive support for the movie is, "Tom Hardy" and "fun", then how can a franchise survive? Tom Hardy can only carry a movie so far. Marvel movies, and as Aquaman and Shazam have shown - Worlds of DC movies, are fun. Venom offers no separation to create a niche that those 2 can't deliver on. There's a certain relationship that Spider-Man delivers that makes any movie he's in draw attention. Outside of the Back-9 in Spider-Man 3, he's always made every movie he's in better. It's what Spider-Man brings - not what Venom lacks.
The Killing Joke doesn't facilitate the necessity of Batman to Joker, but rather puts the Joker at the forefront of another story - graphically. I don't see how this is a counterpoint.
How is Venom even an anti-hero? He serves as the objective protagonist in the movie. Killing a few guys here and there does not make one an anti-hero. See: Superman and Batman in recent cinema. Calling him an anti-hero does not take away from the fact that it seems Eddie Brock has him entirely reigned-in as a full-fledged hero. He "adopts" mankind. He's a tool for heroism at this point and nothing else.
Box office aside - the importance will be about storytelling and truth to character. If The Joker is painted as some sort of anti-hero, it will be equally as bad as Venom. We've seen that villain-centric films can prosper with The Dark Knight and Thanos.