I have experienced the same issue as you. It seems that Stardock can't get their issued in v4 fixed with HDR, they just keep making excuses and not providing solutions. I suspect that as soon as v5 comes out we'll be abandoned and stuck with broken v4.
Funny thing is I have v2 on my other machine and it works perfectly fine. No issues with HDR, folder view doesn't bleed through to full screen apps, and text in menus is legible.
I wish I could use my v4 key with v2 of the application.
I guess they don't believe in the mantra, "If it ain't broke don't fix it."