Friday The 13th Part 5 - Unsung gem of the series?

It's pretty clear the series hit a stride with Parts 3 and 4, then 6 and 7. These feel like the films that set up and use the Jason archetype that the series is best known for.

So why is part 5 generally considered an odd one out in that run?

Is it merely the Jason copycat angle?

Personally I find it up to par with the other Friday sequels in that era, I may even prefer it to Part 4 and 7.

Ethel's son on the motorbike, what was going on in that scene? Freakin' hilarious.