Let me explain to you a thing:
There’s a difference between shipping the characters Snape and Hermione than shipping the movie Hermione with the movie Snape.
As for the age thing most people picture Alan Rickman in their head as Snape. However, book Snape is a LOT younger than movie Snape. When Alan Rickman appeared in The Philosopher’s Stone, he was around 55. Snape is only 31 in the first book.
I believe that Alan portrays Snape wonderfully, but a lot of people get their panties in a twist over Snamione just because Alan Rickman is old. Alan Rickman is 44 years older than Emma Watson, whereas in the books, Snape is only 20 years older than Hermione.