I have a ranger with 10 WIS. Technically he's a Revised Ranger but I don't think it matters for this question.
I was doing some level advancement planning and read ahead to his Level 20 ability, Foe Slayer:
At 20th level, you become an unparalleled hunter. Once on each of your turns, you can add your Wisdom modifier to the attack roll or the damage roll of an attack you make. You can choose to use this feature before or after the roll, but before any effects of the roll are applied.
This will give my ranger absolutely nothing. He will also not get any new spell slots or spells. Am I right in saying that the only thing he will get is a new hitdie? He can't even multiclass due to needing both Dexterity 13 and Wisdom 13 to multiclass both in and out of Ranger:
To qualify for a new class, you must meet the ability score prerequisites for both your current class and your new one, as shown in the Multiclassing Prerequisites table.
Am I reading this right? What's the best level up option for a Ranger 19 with 10 WIS?
Just a reminder, my question is not about getting to level 19. It's about getting from level 19 to level 20.