I couldn't agree more. To me, it feels like it goes on for so long that you've just watched an entirely new movie, which you pretty much do, but it's not like the tl'dr version it's the actual movie. It also kinda bugs me that it suddenly becomes modern 1950s looking. To me, that would be like if The Nice Guys, set in 1970s LA, suddenly had a 2017 dream sequence, which would completely kill the vibe for me. I absolutely LOVE it on it's own merit, because it's a gorgeous sequence and displays so many amazing things at once, but I'm not entirely convinced it belongs in this specific movie.
That being said, I have no idea what they could've done any differently.