I think it's fair to be sceptical about some of the comment coming from the UK defence sector - much of it seems aimed at encouraging an increase in spending without first improving the (incredibly wasteful) state of defence procurement.
The comparison with WW1 is instructive in that regard. Then, the view that conflict with Germany was inevitable was surprisingly widespread - particularly in the wake of Agadir, though it had been steadily building over a couple of decades. It's just that the nature and scope of the conflict that caught them by surprise - a land war rather than being primarily naval.
Vast amounts of money had been poured into building up the navy (always controversial - Gladstone's final premiership was ended by his opposition to a 'vortex of militarism', and Lloyd George and Churchill made similar arguments 15 years later) but those very expensive warships spent most of the conflict at anchor. Most of the pre-war spending was essentially wasted.
If we were to double our defence spending today, we might well end up pissing it up the wall on the same old mix of Trident, aircraft carriers, helicopters, unworkable AFVs, and the most limited carrier variant of F35 when the actual threats are cyberattacks, disinformation, and a variety of hybrid attacks.