Enchanting any netherite or gold tool will never give you efficiency V, no matter how much you try, even though netherite has an higher enchantibility than diamond and gold has the highest enchantibility and both are supposed to get efficiency V from an enchanting table (source: minecraft wiki)

Steps to Reproduce:

  1. Create an enchanting setup with atleast 15 bookshelves
  2. put a few stacks of lapis in your inventory and give yourself a lot of xp
  3. enchant a netherite/gold tool (pickaxe, axe, shovel or hoe)

Observed Results:

You will never get efficiency V no matter how much you try

Expected Results:

You should get efficiency V sometimes