Earlier quoted context omitted.
That’s by design. The council is kept small and all permanent members are nuclear powers. The ability for Russia and the US to veto each other’s foreign policy spats and agreeing-to-disagree is the reason we’re still alive today.
There are more nuclear powers now, so shouldn't the security council permanent membership be expanded? We're not in 1945 anymore.
All of the countries that could - and would (given the right kind of existential threat posed by another) kill a few _hundred million_ people in even a limited exchange are on the council.
There are other, non-nuclear states that could cause similar (To an extent it does come down to sincerity - I’m not concerned about India being a nuclear power despite it bordering Pakistan and PRC: I have faith in India’s democracy and stability to use their power responsibly (Kashmir is another discussion) - but I don’t extend that to DPRK who are clearly using it to avoid a Libya-type situation but who may end up using it anyway given the inherent instability of autocratic dynasties.