Currently since nether creatures are unable to breed they will continue leveling while other creatures “loose” levels each time you breed them. This creates a lopsided party and makes it hard to determine a good realm level (and also reduce resource income for the group). It also makes using existing nethers for new groups undesirable.
Could we get a punishment (or even as default) where the nether’s level is based on the average of the party’s level? Gene strength is already treated that way and it is not that far-fetched to apply the same to the nether’s “experience”.