The overhead of the TLB and page walks have been increasing over time as memory gets larger - 4kb pages made sense in some contexts but not others so page sizes are now increasing, and this is complicating APIs and kernels. The complexities of huge pages on Linux being a case in point.
I suspect he may also be thinking of the prevalence of one virtual machine:one app in the cloud, where you can argue (and the Seastar guys do) that the process abstraction just slows you down because the unit of isolation is the VM anyway.