Now it's 2023 and I have the very same issue with Vanilla and Pure BD Craft.
Previously it run well with Radeon RX 570 4GB, but now my RTX 2060 Super 8GB sucks hard.
Recently I changed my system SSD to Samsug 980 512GB, so I have a new, clean Win 11. Unfortunately this issue remained, that makes me sad.
I checked JolyCraft, which also behaves in similar way: there were only ~30fps with 3-4% GPU and 54% VRAM usage in a small village at night, which went up around ~40fps on daylight with the same low HW usage.
Furthermore Minecraft doesn't save the last used texture pack, it resets on every application start.
I suppose all these issues related to Minecraft itself.
BR,
Northbeard
