Yup, I definitely think the fandom has a huge influence. I remember when finishing Buffy I immediately went to the internet to see what everyone else had to say about it and do something about all my feels lol. The first thing I was totally surprised by was all the love for Spuffy and Spike, neither of which I hated (although Spuffy made me uneasy during season 6 & 7), but neither stood out to me when compared to other relationships and characters in the show. Fourteen year old me thought the show pretty much drove it home that Buffy and Spike being in a relationship wasn't meant to be and really shouldn't be, and that Spike did a great thing sacrificing his life for everyone, and that was that. It was especially jarring because the discussion boards that I first visited were very pro-Spuffy and Spike (and also anti-Angel and anti-Xander, my favorite male characters 🙁) where people were saying that Spike was the only good character, that years from now Spike and his arc would be the only things remembered from the show, etc. This, combined with rewatching the series, reading debates and essays about the disturbing aspects Spike and Spuffy, made me grow to dislike them.
But on a positive note, the fandom did make me appreciate Faith, Dawn, and Riley more! I already liked Dawn and Riley, but seeing the largely senseless hate they received made me more protective towards them. I would still hate Faith if it weren't for Angel and the fandom, but seeing her complexity in Angel and reading others' interpretations of her and her relationship with Buffy made me really enjoy her character and story.