Defensive metrics are notoriously finnicky and need massive sample sizes for true talent evaluation.
Since 2013, the only first basemen with >3000 innings worse than Abreu in UZR/150 are Encarnacion, Morrison, Lind, Chris Carter, and the corpse of Ryan Howard.
In 2018, he had the lowest UZR of any qualified first baseman despite playing about 100 innings less than the rest.