Venom as a creation in the comics during that time was incredible.
He was amazing because of what came before. Spider-Man’s use of the alien costume, slow realization that something about it was odd, and eventual discovery of its true nature made for great storytelling. It was simply too good to be true, as it seemed the moment he received it on the Beyonder’s world. When he went to the Fantastic Four and Reed was examining it… well, that’s all burned into my memory because I was in full on fan OMG mode. Again, it was great storytelling at the time.
In the first issue of Web of Spider-Man, when the symbiote comes back, well that was just as awesome. It really set the stage for Venom. It sure seemed like he had finally rid himself of the costume once and for all. Issues later, when Spidey would have these moments where his fundamental spider-sense wasn’t working but he knew something was off… that created an amazing sense of dread for a character who always seemed in control. Suddenly, he could have a real sense of the unknown. Venom’s appearance, as created by Michelinie and McFarlane, was absolutely amazing at that point. Here was the costume, paired with someone parallel to Peter for years who had a beef that was again, well written into the story of Spider-Man, who pretty much seemed like his greatest possible foe! As @wallapuctus notes, the symbiote knew everything and Brock hated him.
Take all of that away, and there’s just no venom to Venom. While the character and the costume and its offspring have made for some good stories (I liked Carnage when he first appeared…), and I’m totally fine with the anti-hero in general, it’s Venom as misguided angry hateful creature that allows all the rest to happen. In this film, you will have none of that, and it can’t possibly hold up.
They could’ve co-opted the Secret Wars story and put it into Infinity War tbh. Have the Iron Spider suit get destroyed and find a way for him to gain the symbiote. Play that out in another Spider-Man film. Use what you have that made the character so great in the first place… but that’s not Sony’s style. It’s a mess.