This. If you do anything write-intensive at all, it's not only slow, but extremely failure-prone. We moved to the BeagleBone Black, and most recently, Intel NUC, to resolve these issues.
Agreed. I was planning to set up a pi as a media server sharing out a synced Dropbox folder, but the long term reliability of the storage made that impossible. Sure, you can attach USB storage (and that should be pretty fast with the Pi4) but then the tiny form factor is lost.