Lack of RNA nucleotides obviously still no evidence or theory can explain the abundance needed, pools of it for millions of years to suport random self assembly into RNA of usefull composition followed by self replication for million of years with no membrane or safe environment on a very hot earth, hardly possible of carrying life as we know it.

But its moving forward, some even propose pre RNA molecules evolving into RNA with some catalytic effects as temperatures droped etc.

I gladly follow the progress, but i am naturally skeptic to evolution and big bang, it´s being taken for granted by many but we should not forget it is still theories that carries a lot of flaws :)