Vanilla data pack disabled after upgrading a world to 1.14.3 (items do not drop, fishing doesn't work, no advancements, ...)

When upgrading a world to 1.14.3, blocks do not drop when mined. Animals when killed have no drops.

Affected world provided by Infern Pie: https://drive.google.com/file/d/1DKcMbN4154RQspuoAuru15EjoAGVJXIb/view?usp=sharing

Seems to be caused by some data pack loading issues that prevent vanilla loot tables/advancements from getting applied.