Early JN Koharu was a bit like Misty and more entertaining. She wasn't amused by Ash and Goh's antics and would call them weird, and make comments like "Oh great there's even more of them now..." when seeing more and more of Goh's Pokemon populate Cerise Park. Eevee's introduction is what truly made Koharu dull, imo, especially since the show never went anywhere with it.
Goh... ehh, I mean, I feel like just as the writers barely did much with Brock's goal of becoming a Pokemon Doctor/Breeder, Goh's goal never felt all that substantial or interesting. What was frustrating is we finally had a main character that was catching a wide variety of Pokemon from regions all over the world, and aside from the rare situational instance in a handful of episodes, the writers hardly ever bothered to tap into even 1% of the potential the premise had to offer.
The biggest issue I have with JN is really, the series had a lot of great ideas and opportunities to do things the anime had never done before, but the writers took it in the most predictable and blandest direction imaginable, including with Goh and Koharu.
