A lot of people answering here and pointing to wars fought since WW2 don’t seem to understand what conventional warfare is.
Conventional warfare is fought between two states with the goal of forcing one side to surrender. It is preceded by a declaration of war. Conventional weapons are used, as well as conventional battlefield tactics.
If one side isn’t a state and thus cannot surrender, it is not conventional war, it is instead unconventional war. The reason for this is that only a nation-state can deploy the kinds of resources it takes to build and maintain a conventional military. Materiel needs construction and maintenance, supply chains are big and unwieldy.
Conventional war appears to have fallen by the wayside. The nuclear threat indeed seems to be working. Sure, we fought something that looked like a conventional war in Iraq, but it looked like nothing that’s ever come before it. The time frames for battles are measured in days or even hours rather than months.
Warfare is being conducted according to different rules than the old conventional paradigms. It’s not inconceivable that another total war could be fought, but there’s a good chance that a serious nuclear exchange will take the fight out of both parties.
So while it yet remains to be seen, I’d say that sure, warfare has been changed so much by nuclear weaponry that we can call it a new age.