..... they adore Friday 1 as a classic and it doesn't have Jason in it as well, he is only briefly mentioned in it same as part 5. Why does part 1 get the pass in hindsight but this one doesn't? I've never understood this. Part 5 isn't any better or worse than part 1, both are simple straight forward 80's slashers that were only trying to showcase gore, tits, and some chase sequences.... that was it.
Who knows? A lot of people are stupid. I love Part 5.
It does remind me of the movie 'Scream' where the killer asks "Name the killer in Friday the 13th" and she screams, "Jason!" and he says "I'm sorry, that's the wrong answer. Jason didn't show up until the sequel."
With regards to your question. F13 was the beginning of the franchise, they weren't originally meant to be Jason films. It was due to the box office success that they made sequels and since Mrs. Voorhees was killed off they decided to use the shock ending to their advantage and bring Jason into the fray. It's easy to give the film a pass in that respect whilst Part V was a deviation after Jason became the face of the franchise.
Put it like this. If Halloween III: Season of the Witch was the first in the Halloween franchise people wouldn't have hated it because the expectations for a Michael Myers slasher would never have been there.
This is the double edged sword of sequels, remakes and so on. Due to the popularity of the I.P. you already have a built in fanbase and that helps make the films profitable, the downside is that the fanbase in question have certain expectations.
Many decent films have been dragged over the coals due to failing to meet the expectations of the franchise fanbase. Halloween III and F13 V are two examples.
I like F13 V and Halloween III but it is what it is. The fanbases back in the 80s wanted Jason and Michael films and any deviation from that was a sin.
The original F13 film also gets bonus points for being the original. You'll note that in almost every case that the original film in most respective franchises (in particular horror ones) has the highest rating on IMDB. They get bonus points out of respect for being the origins of the franchise.
That's right, Cunningham never wanted to make any sequels to it in the first place and only did the first one to finance other projects. He didn't even like the Jason idea.