I don't want to see venom or carnage in this series be cause
1) we have already seen venom
We saw him for less than 5 minutes of costumed screen time. We also already have seen Spider-Man's other two archenemies' (Goblin and Doctor Octopus) and people seem open to having them return.
2) can't do carnage without venom although it would be interesting to see him
Same reason as before.
3) 2 symbiote villians just seems boring
Venom is what Peter fears he could have become had he gone to far, as Carnage is what Eddie could become. Peter is as responsible for Venom, as Eddie is for Carnage. You could have both characters in the same film, using Carnage's appearance as means to resolved the conflict between Peter and Eddie, maybe recreating the ending of maximum Carnage with Venom seeming sacrificing himself to stop his symbiote son.

