Distant Horizons has updated to 2.3 recently and requires oculus 1.8.0, which confusing me because I only find oculus 1.7.0 here or on modrinth.

Yeah, that's because Oculus is a port of Iris, Iris already has a version 1.8, the only thing you can do now is wait for the Oculus dev to update the mod to 1.8

Bringin Oculus to the stand of Iris 1.8 would be neat in general since the Iris 1.20 versions at least the NeoForge/Forge build are somewhat "dead" or paused and the early versions that were released miss many compats Embeddium and Oculus have (for example create compat and Valkyren Skies Compat).