My daughter couldn't wait to turn 18 and was so excited the cruise that she was able to finally do Palo's -- and then confessed to us later she didn't like it. She's done a brunch or two since, but is not interested in another dinner -- the food was too "fancy" for her and she didn't like the selections. Fine with us -- costs us less and more intimate with just the two of us
The whole reason we like the adult only restaurants on both
DCL and other cruise lines we have been on is because it is nice to be in a place where the people at the tables are actually there for the food experience! Kids don't care about the food or the experience -- they just want fun stuff to eat and I think a place like Palo's would be way to confining for them.
Other cruise lines (like Pinnacle Grill on HAL) have age restrictions also for some of their dining experiences -- and most start at 21, not 18! So DCL is being generous.