@DragonCoffee In the past, we've kept the old design for a while before retiring it, but with all the backend changes, the old design was incompatible and would have required too many fixes to make it worth keeping.
The header is a bit larger than it used to be because it was designed for widescreen monitors. I will be reducing its file size shortly to increase page speed, and I'll see if I can't shave a few pixels off while I'm at it.
-- Edit --
I've made a few tweaks so far:
Fixed article image alignment on homepage
Fixed editor toolbar background
Reduced header height