I know fear is in the eye of the beholder (it all depends on many factors - personality, temperament, upbringing, religious beliefs, even gender, as slasher films tend to frighten women a lot more than men) - but I emphatically reject the idea that "old" means "less scary". The Exorcist is all the more effective for having practical effects, make-up, and so forth. And it is a serious examination of faith, grief, fear of teenage sexuality, and a lot of other things. If it doesn't scare or disturb you personally, that's one thing, but it is a genuinely great film featuring astonishing direction, performances, and so forth. Objectively and in terms of influence, I consider it the greatest horror film ever made. And yes - it is still impacting modern audiences. A rerelease screening I attended two years ago featured at least a dozen terrified walkouts and afterwards I saw several pale looking faces in the audience, especially the younger people who'd obviously gone to see the film, aware of its reputation having not seen it before.

Not everyone will be scared by it, but that it is an influential classic that still disturbs people to this day is inarguable.