I agree that the build up of the RN/RAF F-35B force is painfully slow! However, some of the most important carrier roles do not involve large numbers of jets, but are helicopter centric like Anti Submarine Warfare or Littoral Maneuvere. It would appear the UK has committed ASW capabilities to NATO, and we did provide the flagship for Exercise
Deep Blue in 2014, and
Deep Blue II in 2016.
On the other side of the World, ASW has been identified as a likely mission for JMSDF 'helicopter destroyers' -
JMSDF 'carrier' to escort US supply ship.
This is where the Izumo can be useful. The carrier is especially adept at working as a anti-submarine warfare platform, with the ability to create a large screen around the ships it protects via its embarked sub-hunting helicopters. It can also provide mine sweeping, surveillance, command and control and other capabilities in addition to additional fuel carriage—especially aviation fuels—which can be pushed to other assets like guided missile destroyers.
In future Japan will most likely have F-35B launching of their decks as well. Logistics are universal. Equally, they are universally at risk. Submarines and Air to Surface Missile armed aircraft are in the hands of many aggressors.
Land based forces, including aircraft operating from land bases, still depend on seaborne logistics. See:
The RAF sets sail for Estonia
Can you imagine this type of conversation:
You just need a ship with lots of deck space and a squadron of helicopters....
Do you think that ship is going to be a bit like a carrier?
Well..... so what?
The enemy will see her as a priority target for air attack!
Give her an escort then.....
She could carry fixed wing aircraft, and stop the bandits long before any ship can! Which would have been a better plan anyway - archers not arrows.
But we do not need carriers - no use ever..
What about protecting ships full of spares or support equipment, or an LPD?
They are expendable, and cheaper to replace than jets...
God willing, we will not face a cataclysmic conflict with Russia or China, but the Geopolitical posturing and deterrence we saw in the violet peace of the Cold War, limited war such as the Falklands or Gulf, or actions to try to cool a conflict in the developing world that involves third parties (eg the eighties tanker war), or interventions on humanitarian grounds (Bosnia/Kosovo/Sierra Leone) or on behalf on UN resolutions (eg Iraqi no fly zones, Afghanistan post 9/11, or Libya).
Unsurprisingly, NATO has carrier related initiatives:
Affirming and Preserving NATO Air Power from the Sea