Yes, same! I didn't expect it to need so many tricks to implement. Your intuition is correct, the most resource-intensive part is the blur bit of the backdrop-filter. The higher the blur value, the more neighbouring pixels need to be "consulted" before rendering. Another resource-intensive aspect is continuous repaint as you scroll or as a video background changes the look of the glass.

And sometimes it's 5 layered tricks just to "center" something.

Not anymore! We live in the golden age of display: grid; + place-items: center;