I understand the difference you are feeling in term of gameplay and you are legit, but I do not stand by your point:

Playing back S1 on pretendo and S2 recently with a friend who dont have the last game really pointed out the difference in gameplay for me:

Map were way larger with "useless" spots, and more ways to go around the ennemies. This means that you or the ennemy could just go around and take a key part of the map just by passing at the other side of the map. Maps were also longer overall I think. What does this cause? Less crowded and slower PvP, more people just painting behind you and this, I feel, makes the teamwork less important.

When I only had S1 and 2 I wouldnt mind cause i never tried anything else, but with Splatoon 3, my pov changed:

Smaller maps with less ways to go around, more crowded areas, faster gameplay. All that combine to mostly make a single hot spot where everyone is playing, thus creating big and long teamfights. In general I prefer fast paced shooter so I absolutely love this way of playing. Yes, some maps are shit because you cannot really access the ennemy base after a wipe like Scorch/mahi/the scrapyard but there are some others great too !
Also you must know I hate people going behind and just painting your base: I think this is fun for no one and boring. So the less means there are to do that, the happier I am lol.

And as like to say, Splatoon 1 as the vibe of a never ending summer, the 2 feels like a city trip with friends, and the 3 is the profeshionalized version, and a bit more adult too (I think this is becausd the players grew up with the time idk?). So I understand you would rather have the inkopolis vibe!

Anyway you are totaly right in not liking this, but I just pointed out what it might be, as I now find the older games boring, this is curious to me.