Two people dancing ballroom-style is always gonna look the same, but as far production design goes, they’re referencing two different movies (albeit both Fred Astaire movies).
La La Land took the twinkly lights that reflect on a black surface from the “Begin the Beguine” number from The Broadway Melody of 1940:
The Shape of Water took the obelisk thing in the background and the striped floor from the “Let’s Face the Music and Dance” number from Follow the Fleet:
They’re not alike to each other - they just both reference classical Hollywood, but while La La Land echoes just the set of one movie, The Shape of Water also copies bits of choreography (mostly “Cheek to Cheek” from Top Hat) and Ginger Rogers’s costumes from other Astaire movies and then turns the reference on its head with the monster, so really, it’s like comparing a sundial to a Swiss watch. More craftsmanship went into the latter; the former is just a shadow.