Some mods simply remove vanilla DFU (DataFixerUpper) to save memory.
This breaks our entire compat layer for old schematics rendering them unloadable.

Solution for client is to notify the player onWorldJoin/on old schematic being loaded and close the buildtool gui.
Server should crash during sided setup

something like this should be in DataFixerUtils
public static boolean hasVanillaDatafixer = DataFixesManager.getDataFixer() instanceof com.mojang.datafixers.DataFixerUpper;
https://github.com/ldtteam/Structurize/blob/version/1.16.3/src/main/java/com/ldtteam/structures/blueprints/v1/DataFixerUtils.java