I'm having the same issue. I shot some drone footage at 1080p 1920x1080 60fps. The only adjustments I made were to use a color preset of Light-Darker.
It took 1 1/2 hours to render 5 minutes of video. It took over 12 hours to produce a 20 minute video. It took almost 2 to render an 8 minute video.
I have a ryzen 7 2700 processor, a gtx1060 Nvidia with 6 gigs of onboard ram along with 32 megs of ram. This is not a slow computer by any means.
I've tried with and without hardware accelleration and various settings. I'm producing the same bitrate and fps as the video. There is no reason for it to take this long.