WorldEdit for 1.21 (7.3.4) Requires com.google.guava:guava:{strictly 32.1.3-jre} while owo-lib requires com.google.guava:guava:33.0.0-jre, the former matches what minecraft itself has while the latter does not.

Checking 1.21's .json file:
"name": "com.google.guava:guava:32.1.2-jre"

Yes somehow both are mismatches (even though worldedit claims it matches), but owo-lib is very much mismatched, which makes any compilation using both to fail.

Also of note: fastutil is also ahead: it.unimi.dsi:fastutil:8.5.12 in Minecraft & WorldEdit, it.unimi.dsi:fastutil:8.5.13 in owo-lib

Edit: seems i am mistaken, the root cause is not owo-lib but io.wispforest:endec and related packages

Closing this issue: WorldEdit seems to have recently changed the way their versioning is done, and accidentally(?) setting some version requirements to strict that weren't before. Solved on my end by simly using

{
    exclude group: 'com.google.guava', module: 'guava'
    exclude group: 'it.unimi.dsi', module: 'fastutil'
}

on WorldEdit.