With the 1.21 branch, entering a world gives the following error
[Worker-Main-10/ERROR] [net.minecraft.world.level.storage.loot.LootDataType/]: Couldn't parse element ResourceKey[minecraft:root / minecraft:loot_table]:alexsmobs:gameplay/seal_reward - No key value in MapLike[{"type":"minecraft:loot_table","weight":4,"quality":-2,"name":"minecraft:gameplay/fishing/junk"}]
After greatly increasing the weight, I can confirm that this error does prevent fishing junk from being rolled.
I saw online that "name" should be called "value". This seems to fix the error and allows junk items to be rolled, but a different warning appears, which I'm not sure how to fix
[Worker-Main-4/WARN] [net.minecraft.server.ReloadableServerRegistries/]: Found loot table element validation problem in {minecraft:loot_table:alexsmobs:gameplay/seal_reward}.pools[0].entries[0]->{minecraft:gameplay/fishing/junk}.pools[0].entries[12].condition[0]: Parameters [<parameter minecraft:origin>] are not provided in this context
With the 1.21 branch, entering a world gives the following error
[Worker-Main-10/ERROR] [net.minecraft.world.level.storage.loot.LootDataType/]: Couldn't parse element ResourceKey[minecraft:root / minecraft:loot_table]:alexsmobs:gameplay/seal_reward - No key value in MapLike[{"type":"minecraft:loot_table","weight":4,"quality":-2,"name":"minecraft:gameplay/fishing/junk"}]After greatly increasing the weight, I can confirm that this error does prevent fishing junk from being rolled.
I saw online that "name" should be called "value". This seems to fix the error and allows junk items to be rolled, but a different warning appears, which I'm not sure how to fix
[Worker-Main-4/WARN] [net.minecraft.server.ReloadableServerRegistries/]: Found loot table element validation problem in {minecraft:loot_table:alexsmobs:gameplay/seal_reward}.pools[0].entries[0]->{minecraft:gameplay/fishing/junk}.pools[0].entries[12].condition[0]: Parameters [<parameter minecraft:origin>] are not provided in this context