S2 has several problems. To name a few:
1, expectations: Nobody thought The Series will be more than a cute girl doing princess stuff. Then we got tons of new and great characters, pretty good animation, interesting stories and the main plot was awesome. Even if S2 would be the same it would still look weaker.
2, repeating the lessons: S1 had to being from the start. They introduced different characters then they had episodes with interactions between them and establishes relationships. S2 does this again and it is not interesting for the Nth time. For example we have several "Cass and Rapunzel can't understand each other bc they are different lol" episodes when that part was done ages ago.
3, the side characters are either weak or randomly get screentime
4, the pilot didn't do a good job to set up the main plot and we don't even get bits to chew on
The only thing clearly superior in S2 is the character animation. The main characters, especially Raps got a lot of new and very expressive and fluid animations. It is a joy to look at the scenes.