Could you elaborate on this? I develop an embedded OS which regularly flashes itself while running systemd (we support two methods: 1. write partition table to disk, write fs header to partitions, explicitly mount fs and write file content to fs; and 2. dd pre-built image) and I have never seen this happen. We have also flashed (via dd) our images onto cards from within Ubuntu 16.04 and 18.04 and never seen this.
In your specific case, if you were using systemd-networkd you could specify MACAddressPolicy=random in your link file to achieve what you wanted.
Likewise, systemd doesn't prevent you from running ALSA instead of PulseAudio. The flexibility is there. Better documentation/best practices would be helpful.
https://bugs.launchpad.net/ubuntu/+source/network-manager/+b...
The problem is of course when you need to do something that isn't supported by SystemD, in which case you're in for a world of hurt as the system constantly fights you.
For example, I had a requirement to make sure some machines randomized their MAC addresses when connecting to untrusted WiFi in Ubuntu 14. Turns out this functionality was broken in NetworkManager and trying to go around its back was a huge huge headache because the system was relentless in checking the MAC of the interface and setting it back to the physical one.
There are other times where it bites you in the ass too, like writing a raw image to a SD card. In the old days you would just dd the image onto the card, but you can't do that anymore because shortly after you write the filesystem header to the card SystemD will notice the new filesystem attempt to mount it, killing off your dd process.
I always try to work with SystemD now because it's so much harder to fight it.