It is right I think that Russia has been selling missiles to the Iranians that would make operating in the Gulf rather riskier if Iran decided it would not tolerate our ships there.
The basic point presumably is that Western armed forces achieve a huge dominance of all battlefields on which they fight, but the strength in depth and capacity to replace is not there. If one carrier gets severely damaged by a lucky missile that is an enormous proportion of next year’s defence budget down the tubes, almost certainly fighting a conflict that does not make votwers at home think that they may be speaking German next year or whatever. Better to have the carrier over-protected than under-protected.
Also, presumably, putting fleet either into the Baltic to protect Estonia/Latvia/Lithuania or the Mediterranean/Black Sea to protect Ukraine/Georgia from Russian intervention must be explicitly planned for. If the navy found itself in those situations again then theoretical Russian capacities to do our ships harm are very great.
Do the Chinese have carriers? Or aircraft in East Africa?