Spectral Currents seem more likely per spectral fish hook the less people that are on your boat. Both my fishing linkshells have been testing this out for weeks. Sure enough the other night when I get a solo boat at the last moment, I have a 100$ spawn rate of spectral currents whenever I hooked a spectral fish. I've been told not to expect that kinda luck every time but hey, can't argue with the results so far lol
So the game mode has been future proofed somewhat to when it's no longer popular to do. Less people hooking spectral fish, but higher chance at Spectral Current when they do, meaning nobodys going to have a bad time.

Don't let people who are there for a different reason bother you if they leave. You aren't as impacted as you'd think!