But that's the thing, Let's Go's water is meant to be seen from a single perspective. You say the water in legends looks tiled now, it would look even more tiled if they used the Let's Go one. In a 3D environment you can't use the same thing. Besides that, the sea water in Legends is different from the rivers and lakes, which looks a lot better, with real time reflections, transparency, distortion effects for stuff underwater, better adaptability to lighting:Nah the water looked really, really bad in SwSh too.
There is no hand crafted element, its a flat plane with some completely wrong reflections and a ripple effect.
The other game wasn't the best but it had exaggerated caustics and shallows which worked so much better with Pokemons toon aesthetic. Id take something like Wind Waker over generated water like they want to use now.
How it looks now, disregarding tiling in the long distance shots:
That aint water
SWSH's water was indeed basic, but it worked better in towns with a more curated use of it