Scorpion should have become like the Reverse Flash for Spider-Man, not a Shocker like goof.
>Venom took his niche
Kinda but not really, Venom is much more the "Shadow the Hedgehog" than the "Scourge the Hedgehog", his design and being mirrors Spidey but he's also totally different, brings his own themes that almost don't even fit with Spidey, and was always more mentally warped and angst ridden moreso than outright evil

Scorpion's "insanity" seemed to present as an unhinged turn towards violence and petty cruelty, which is perfect for a long term antagonist rival for Peter bleeding heart Parker