I have a good rig and I get 20-30fps average on this map. I can get up to 300 on cs_assault and other basic maps.
placebo, Christmas island is definitely unoptimised, and remember that Assault is a Valve map, and its optimised very well actually you probably cant see the FPS difference because christmas island is so dark
The Christmas maps should have already been out of rotation. Just give us a bit of time to get some code pushed, sorry for the inconvenience.
Even original island map has major FPS issues. I get it's a popular map, but even me when a 1080 and Ryzen 7 processor can get down to 40 FPS in certain places. Everyone always complains about the lag on it.