its basically fan service the movie but it's still enjoyable to people who aren't as invested in the series. i watched it with my parents (dad knew a bit, mom knew nothing, i've been in love with the series since i was little) and while they were confused at a lot of the references, they still found the movie to be enjoyable enough.
It's also important to note that the movie lore is VERY canon divergent, cramming in all of the lore mainly from the main 6 games (fnaf 1-pizzeria sim) into a revised story that can fit a movie's average runtime.
the characters are cool and likeable, i like how william afton is played by shaggy, i think abby is a cute character, the visuals are done amazingly, and i still had a lot of fun with this one even if it wasn't as gory as the horror movies i normally love. overall i highly reccomend at least one watch, but if you know nothing about the game, it would be better to do research on the franchise before watching just to get the full experience