So, enough "I told you so." Enough "it was never meant to do that." How about what it can do? Tactical Bomb Truck seems to be the current thinking. Anyone care to think about how HMS Queen Elizabeth might be defended?
There's two parts to your question:
1. Defended from what/who? Against the vast majority if nations, no problem. Against a 1st or big 2nd world nation (like India? Brazil?) with a modern air arm and/or modern sea denial weapons (like anti ship missiles and submarines), no chance of survival. In the latter case she would need to operate cooperatively within a proper carrier battle group. Do you really foresee an RN carrier engaging a significant military power all by herself? Really?
2. If not F-35B what would you propose as an alternative? F-35C? Super Harrier? Rafale M? Super Hornet? Su-33? MiG-29K? What data do you have that indicates any of these would be significantly better at defending her. And equally importantly, capable of defending her while also providing the same offensive capability?
Apologies to the Americans for that question; I understand you couldn't give a ****. Just as long as the UK remains a loyal partner and buys it.
Gratuitous cheap shots from these folks seem somehow appropriate and expected. Wonder why that is. (Oh wait, that was a joke! Yeah, that's the ticket.)