Okay, though that's not the same as the Mac simply being "slow".
Mojave seems to be a bit of a mess. I had to go back to High Sierra on my 2010 Mac Pro so I could use our small NAS server without constant write error messages. The other person with a 2018 Mac Mini has no choice but to copy files they want to work on to the Mac, then copy them back to the server and overwrite the older files. This appears to be specific to the Adobe apps.
Here's the bug report I sent to both Apple and Adobe:
It took us a while to figure out Mojave was the key to the issue, and not the NAS. In High Sierra, with the exact same version of Photoshop CC 2019, I can work directly off the NAS all day, every day without a single issue. As soon as myself, or someone else using Mojave tries to directly access the files on the NAS, writing files becomes nearly impossible for everyone.