What needs to happen here is talk between ATC and operators. Slow as possible in cruise and high-speed descent is only one way of doing things, IMO not the most efficient, fuel-wise, and it appears not the easiest for ATC. A reasonable-speed cruise and reasonable-speed descent would probably be better.
If ATC tells us officially what annoys them, I'm sure the pilots/operators could adjust their modus operandi to fit in a bit better.
if the fixes were further out it would be less of a problem, because most of the descent would be after the fix
As mentioned, in some types, the descent is where a lot of the time is lost. If there is less descent, less capability to go slow (as well as less time in cruise). We see this on the Julim for 03: the higher crossing altitude leaves us less time to get slow before the FF.