Haha...  Maybe no need to take it to the extreme.     For now, bitcoin is doing fine on POW, as are many other coins.

But honestly, I do fully believe that mining is going to be the Achilles heel of crypto going forward, as Moores law and the advancement of hardware technology remain a constant challenge.  The goal posts are constantly changing and no tech is future proof.  There is a very large financial incentive for people to exploit and take advantage of systems built for older tech/hardware with their newer, faster, more efficient machines. The time from concept to completion will also continue to drop as they move  beyond the limitations of ASIC's and combine technologies that can be modified or programmed as needed.  The cost of doing so will also continue to drop.