Linux is not a monolithic system. It has a monolithic (sorta) kernel. There's a big difference. You're arguing monolithic kernels vs. microkernels. Microkernels didn't even exist when UNIX was invented, so no, they are not representative of "Unix philosophy". "Unix philosophy" is merely about the user-space tools you use to do stuff, since back in 1970 all they had was the shell (sh), and various tools like grep, ed, awk, etc., to do things.
It's entirely possible to have a microkernel with a Unix-like system; HURD attempts this. Microkernel vs. monolithic is an entirely separate issue.
I think the parent poster is talking about the userspace. A Linux distribution like Ubuntu that uses systemd, GNOME, and NetworkManager is certainly monolithic compared to Slackware circa 1999. NetworkManager alone is a pile of garbage that goes completely against Unix networking conventions, for IMO no good reasons. OpenBSD's approach to integrating WiFi and other network interfaces into the existing BSD network management commands is so much better.
It's entirely possible to have a microkernel with a Unix-like system; HURD attempts this. Microkernel vs. monolithic is an entirely separate issue.