The one major issue I have with Splatoon 2 vs Splatoon is the maps. Splatoon's maps feel diverse, interesting, and each one having its own character. Most of Splatoon 2's new maps feel like basically the same map again and again, at least to me - the highlights are the returning maps.
In nearly every other regard I can think of Splatoon 2 wipes the floor with Splatoon, with the inclusion of the inspired Salmon Run being the home run of the package.
I agree that and the changes to some of the weapons.
The new maps have at best two stand out stages but all of them are basically flat and smaller areas compared to the better stages of the first game.
I loved the mini splatling in the first game, but now I can barely tolerate it in part 2. Somehow it feels like they hit it hard with the nerd stick.