My question is how far has decades of cut throat competition eroded the safety and maintenance standards of all airlines?

It hasn't. They're safer than ever.

But keep in mind that while airliners are very robust against all kinds of mechanical failures, human errors, and natural events, they are not designed to withstand battle damage or to have any sort of countermeasures. Their only safety from attack is they fly at high altitude, out of range of small arms.