That makes it suck slightly less, but TM can pretty much never be "fast" the way it works now, with the number of files we all have these days. In the best case, if a folder doesn't change, TM can hardlink to the previous backup of that folder. If even one file has changed, it has to copy the changed files and then hardlink every unchanged file in the folder, so TM chokes on any large folder where even a single file changes often. If you watch with `fs_usage -f pathname backupd`, you can see TM take dozens of minutes backing up the Mail/Messages/Calendars folders, or cache folders with ridiculous numbers of files like Slack's. Any folder with thousands or tens of thousands of files is putting TM into its worst-case performance corner.

Personally, I find TM bordering on unusable for backups these days. Maybe I'd feel differently if I still had a desktop Mac, but with a bunch of files on a laptop that moves around and sleeps, having to tether to a USB disk for several hours to do a backup is ridiculous. And network backups are even slower and frequently self-corrupt, especially over WiFi. The glimmer of hope is that APFS replication has some really cool new features in 10.15. It's clearly still very much a work in progress, and some big parts are missing, but the stuff that's released seems to clearly point toward a future where we can do block-based copies of filesystems or even deltas between snapshots. Which is much better for performance on spinning hard disks than the eternal disk seeking and grinding that file-based backup solutions all do.