The bug

Villagers seem to become willing to breed with the old carrots, potatoes and bread, but not with the new beetroot.

How to reproduce

1. Build infinite village (Screenshot example)
2. Spawn ~16-32 villagers
3. Throw food at them
   → Carrots, potatoes, bread show willingness "hearts" almost immediately. Beetroot never increases their willingness.

The fix

Add a check for beetroot in net.minecraft.entity.passive.EntityVillager.getIsWillingToMate(boolean updateFirst).