This series is literally my childhood. I would definitely recommend for people to watch it. Kanto, Battle Frontier, Sinnoh, and Kalos were the best seasons. I've always loved the relationships between Ash,his friends, and his Pokemon, especially Pikachu, Infernape, and his Alolan mons.
I'm probably gonna get a lot of dislike for saying this, but honestly, the whole "Amourshipping" thing was quite stupid and I'm kinda glad that Serena was booted from the show. Amourshipping was totally one-sided, Serena only caught 3 Pokemon during the entire series, and the only reason why she went on her journey was to reunite with a crush from like 5+ years ago. Everybody thinks Ash is stupid for not remembering her, but honestly if I was in the same situation I wouldn't remember anything either. She didn't get very much character development, and I feel even Bonnie got more CD than Serena did. She just felt like a more shallow version of Dawn and May, doing the same Contest-like stuff without any good battles, and the only times she would battle are against Team Rocket.
Sun and Moon gets a bad rep mainly because of the Amourshippers. Sure, its not the action of XYZ or the nostalgia of Kanto, but it's still a pretty good series (A lot better than Best Wishes!). The characters feel better fleshed out than the past several seasons, and it's a heck of a lot more funny than Best Wishes or XY/XYZ.
The series will get kind of annoying because of Ash never winning a league and his character development getting reset pretty much every region since Unova (At least Kanto through Sinnoh didn't do that.).
My favorite characters are Dawn (Pearlshipping FTW!), Brock, Clemont, Korrina, Mallow, and Kiawe. Favorite Pokemon are Pikachu, Dawn's Piplup, Kiawe's Marowak, Brock's Croagunk, Charizard, Bulbasaur, Squirtle, Sceptile, Infernape, Gible, Snivy, and Greninja.