I agree that Splatoon 1's stages are a bit more creative with their overall layout, but I think that, despite Splatoon 2's more conservative designs, they don't play out similar to one another.
And Splatoon 1 has some pretty unbalanced stages. 90% of the time, in Moray Towers the only area where anything happened was the middle. Usually at the end of a match the main slopes were both the corresponding team's color and so it came down to the rather small middle to determine who wins. Camp Triggerfish had an original idea (the stage being sort of a one-way roundabout design), but that made for some very crapshoot matches. Though it should be said that most of the time, these can be fixed pretty easily, and in the case of Moray Towers, they already improved on it.
But still, if I think of the best S1 stages, outside of Mahi Mahi, they are the more 'normal' designs, like Hammerhead and Flounder.
Having stage gimmicks in some of these stages or just having a creative design isnt a horrible thing to have, it adds diversity in some sense. But i feel the issue boils down to how fair is the layout of the mode for each map? And this is a question that has too many answers to start off with right off the bat because of what "fair" means in the context of splatoon.
I'll use your example, Moray, for instance. In Splat1, SZ was a dual zone layout instead of the single zone layout that we used to have. Most people have jumped on the side of "this is bad" or vice versa. understandably, moray is a bit of a controversial stage because of how massive it is and how cut off the pathways are.
However in splat1 you had these instances:
-A dynamo could instacap either zone with a flick or two in relatively quick fashion
-the same could be said with inkstike
-the most efficient way to take the game would revolve around hard spawn camping because of how difficult it is to aggreesively push on that map alone
-splat1 favored defensiveness for a long time, so the above instances would have been elevated barring the QRSJ meta in late period splat1
Deciding where the objective goes on a map that doesnt change is a very complicated thing to do because of how the main meat of the game changes to conform to that layout. The only way to conform most of the time is by running the same thing as the team that's abusing the flawed placements and designs of the map combo. Moray and pit arent the only ones, Saltspray grants an advantage to right-side peaking if you end up on the left-most spawn, blackbelly RM is super notorious because of that "suicide" pathway being the most optimal way to score a large lead in a very short time span, Bluefin zones (ironically enough) was a map that would have been better off a 2 zone map but the presence of eliters still made it hard to actually push through to the lowest area of the map, Urchin underpass as a whole was completely unplayable because the main entry to mid was an incredibly small choke and the other 2 paths were easily camped which is one of the reasons that map was also taken off the live servers and completely reworked.
Not every map in splatoon can establish a fair balance in object placement per mode, if there's ever a reason to completely block off a certain section of the map because you want to make it harder to pass through certain areas you're better off just re-designing that section of the map or getting rid of it completely for the sake of balanced design. Urchin and pit are the only two maps to see this happen to them because of blatantly glaring issues, I would not be surprised if in the hypothetical Splatoon 3 we get differing layouts for a majority of maps. Which all things considered, would be concerning due to how many maps we already have. I would not at all be against having maps designed only for one mode however, I think linear and symmetrical designs in an arena style layout is fine, but with objective based modes it has shown to be highly problematic to consistently keep this design philosophy intact.
