Yeah, that's known as The Critique. I will admit I don't know much about it, except that some present Hurd developers it is capable of being overcome, given someone puts enough time into it.

The other main criticism seems to be from a microkernel perspective, but we're more or less implementing something that emulates a microkernel plus daemons on top of a monolithic kernel by adding systemd, d-bus, containers with sandboxing, and the like. The best resource I can find addressing the subject is here, which seems to find that the known problems are solvable but we don't have proof without real implementations, but that's from 1996.