I had a look at the file. Overlap removal is what takes the most time, then PS hinting. But only the first time around. Once the Temp folder is established, export takes about 2 seconds on my old MacBook Air (Mojave).
For quicker test exports, consider disabling overlap removal and/or hinting, depending on what you are testing for at the moment. What may also help is emptying out the Temp folder, and reexporting slowly once, and after that first initial export, it should be fast again.
Plug-ins may interfere as well. Restart the app with Opt and Shift held down, then see if exports faster.
Plus, there may (temporarily) be another (unrelated) process taking up system resources. Consider
top -u in terminal or Activity Monitor to check if there is sucha process taking up resources.