That argument could be countered by pointing out how many of the slower battleships were ineffective simply because they couldn't catch their intended prey..
Battleships needed to get within 10-20 miles of each other to throw bullets at each other in a drawn out slugging matches.
Modern anti ship missiles don't care whether you or your target is doing 10, 20, 30 or 50kts, they will fly out to well over 100nms at speeds of up to Mach 3 and get you.
High speed as a critical design feature became moot on the 21 October 1967 when INS Eilat, a 37kt destroyer sailing 17nm off Port Said, was blown apart by Styx ASM's fired from a couple of Egyptian fast patrol boats sitting inside Port Said harbour.
To boost the speed of a T45 to 36kts as per WWII era Destroyer designs, you'd need to add more engines, and that would need more machinery space, and that would need a longer hull, and that would need more power to push it you see the vicious design spiral?
The pre war Fench Fantasque Destroyers could do over 40kts, but required about 80,000shp to do it. The equivalent British Tribals could do 36kts on half that power.
The power vs speed curve for ships is not linear, it's like a hockey stick, and 30kts sits nicely at the optimum point at the foot of the up slope.
Anyway, I digress, speed isn't the asset it was once. As you point out, missiles and helicopters negate the advantages to a fair degree.
The only real necessity for high speed now is created by the small quantities of ships available to the RN. Being required to cover a larger area because of a lack of ships would make higher transit speeds useful. But I suppose thats always going to be a problem given that the RN has to cover the same areas it did a decade ago with an ever decreasing pool of ships to do it with.
Higher transit speeds use up more fuel and we're pretty much all out of tankers at the moment with no sign of any new ones in the forceable future.