[Bug] Very long load time on first world join

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Bug description
Loading into a world takes a long time. Around 10-20 seconds. It's way too long. Loading a second time into a world is quick.

Fabric or Forge
Fabric 0.17.1

Mod version
Celestial 2.0 1.19.4-1.20.4

Game version
1.20.2

Other details
I tested it on Hyper Realistic Sky. Loading a world the first time when Minecraft starts just takes ages. Maybe there is a way to load Celestia on Minecraft run-time?

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Or maybe there is a way to load it faster.