It isn't a downgrade in performance with no trade off though. As it looks better with the new Ultra+ settings. Whether the visuals justify the performance hit is up to the individual.
I'm not impressed with this update at all. It runs much worse than the old version did, like half the framerate, even at regular ultra settings and with RT disabled. On top of that, I don't see much of a visual difference over the old game, which already looked quite good. DLSS 3 does improve performance a lot, but it's still worse than the old version and doesn't always hit 120fps. There are also some clear visual glitches like stretched textures on some foliage, on top of mod incompatibilities. It's a good thing GOG lets you roll back updates (unlike Steam).
One of the Cyberpunk updates was like this too and the low performance turned out to be due to the screen space reflections setting, but that doesn't improve anything here.
They use a dx12 wrapper api so it's not a proper dx12 implementation which would have required more work. The update itself should have taken more time. They got it right in cyberpunk eventually, it just happened the development on this was stopped then restarted and it had already been delayed before once.The DX12 executable is so very clunky. I've had no less than 6 different crashes just changing graphics settings. Even with ray tracing turned off it stutters. DX11 executable remains smooth. Same Ultra+ settings without ray tracing.