oh I dunno as it is a bit complicated. Seneca wouldn't have said anything against religion - I mean if he had he'd have been forced to commit suicide. and anyway to speak against religion would have been against his philosophy and politics.
Seneca was against superstition and popular beliefs but had a lot of respect for religion. Religion at Rome was led by the senators and the emperor in the form of cult practice and ritual. It was not about superstition or about beliefs. It was more about togetherness, festivals, processions, belonging etc
but these quotes are interesting as they come from people in our own modern times who see all religion as bad and the secular state as good. there would not have been this separation in Roman religion. so I guess it is a good quote for us but Seneca would never have said that.
Seneca is one of my favourite people and I think he is great for us - thats why I'm putting in my penny's worth as like him I think people need religion - his type anyway - not the superstitions and beliefs part of modern religion though as these can be very isolating
edit seneca may have said superstitions are regarded as useful by the rulers and he may have been talking about superstitions re death and the afterlife...and this has been been changed in our own times to say religion is regarded as useful by the rulers etc etc