As a fellow level 40-something, I don’t think that reaching level 60 is mandatory in any way. If you’re learning Japanese outside of WaniKani, especially reading a lot, you’re not only likely to come across the remaining WK kanji, but also learn ones which are not in WaniKani.
The rest sounds like you need a break. Not slowing down and blaming yourself for the lack of tempo or motivation, but just honestly taking a break. For me that helped with motivation to continue learning. Just hit that vacation mode and go feed ducks in a park .
From a more meta perspective, it might be worth considering Anki or another SRS with lesser cycles than WaniKani. What I noticed is that WaniKani’s constant flow of reviews can get fairly overwhelming easily. If you have a couple of decks in Anki, for instance split into themes, it helps with managing workloads.
I went through a period like this as well. What helped was to stop adding new items, and work out through the existing reviews. Kept it like that for a few weeks until the daily workload was low enough. At that point you can consider switching to vacation mode for a week or so to recover. After that you’ll feel like new.
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