The British military problems and resulting inadequacy of British military policy can be summarised quite concisely in my opinion:

Their willingness to tax the rich's incomes is not sufficient to fund a military which meets the military-related grand strategic ambitions.

They want to be a great naval power, but can only afford a small fleet with tiny numbers of nuclear submarines and medium-sized carriers. They want to be able to bully, invade & occupy in U.S: style with minimised KIA and degree of improvisation, but cannot afford an army or air force (including support assets such as plenty tankers and heavylift aircraft) to do it on their own.
Meanwhile, playing lap dog and following the Americans everywhere has been understood to be superfluous.