I don't know if I would call myself a die hard fan or not, I mean, I love the series and have played/collected a lot of it but that doesn't mean that I have seen or done everything that they offer. There is only so much time in the day and there are only so many things that you can do before you get a little burnt out and that means that with all of the content available it would take me forever.
And new stuff comes out all of the time anyway.
On top of that, for me personally, my favorite is original series. I have seen it multiple times and it has the best writing imo and pacing. But in general, the first five seasons have well written stories, funny moments from Ash doing stupid things and it introduced me to world of Pokémon.
On top of that you have Tracy’s temporarily replacing Brock. This led to some good stories and it was nice seeing Ash growing from a rookie to good trainer.
The only downside was that Misty is more of a side character than a legitimate Pokémon trainer due to her so-so character development. It isn't until later that both Misty and Serena become more original. But fans had to wait until SM for that to happen.
The wait was worth it.
One is a tomboy who stood up to her sister's verbal abuse, and latter showed actual growth/ independent development from a girly girl who didn't know what to do to a more matured girl who stood up against her mom's wish and followed her dream as a Pokémon performer.
Sure for Sun and Moon some of the character designs are horrid. And I have yet to find anyone that thought Rotom was anything less than obnoxious, but the animation is fantastic.
Also the story would be better if they could introduced a new groups to replaced Team Rocket, and would be even better if Ash didn’t have to get up his best Pokémon for newbies in Johto season. The worst episode in the show has to be the gym battle vs Liz and Tate in the 3rd generation. People criticize the season for a couple of reasons: lackluster characters, lack of character relationships, as well as Ash turning into a different character.
I enjoy Sun and Moon because it is a lighthearted and fun contribution to the series.