The Sinister Six are originally Doc Ock, Vulture, Kraven, Electro, Mysterio, and Sandman. Spiderman 3 attempted to set up the Sinister Six as part of Sony’s doomed bid to establish a Spiderverse, but Homecoming hasn’t really done that – of the six, only Vulture has been shown, and it looks like Scorpion will be the villain in the next movie.
And sure, I think Marvel could pull off the Sinister Six, in the long-term. It’s important that the villains have individual pasts with Spiderman so their decision to team up against him makes sense, so you can’t do it right off the bat. But as I’ve said before, the key thing is making sure they’re all part of one story as opposed to six stories in one movie.