I can kinda vibe with you about 'potential' if there was a villain in the ASM2 like Loki in the Avengers. Someone with charisma - that fans love even though he's a villain -
But through 2 movies we don't really have a Spidey villain that fans love.
The Lizard wasn't really that memorable.
I actually liked Electro but everyone hated him
The Green Goblin was great for the most of the ASM2 movie. But once he turned full heel, I didn't find him to be likable.
The Rhino- really?
Toomes - can't say - he's pretty much a mystery.
Sooner or later there has to be a villain that shows up in the Spidey movie verse that can anchor the Sinister Six team akin to how Iron Man anchored the AVengers.