I’m seconding the advice to try KaniWani/KameSame now, if you regret not doing them when you were going through WK in the first place. You can start at level 1 there and just do the lessons as you please. You could even set it to burned items only if you want!
If you do try KaniWani/KameSame, it would probably help you recover a lot of your lost knowledge, and would help your review backlog on WaniKani be less painful. You could always start with that and see how you feel about diving back into WK afterward?
As others have said, you probably don’t “need” WK, at this point, but I understand wanting to complete it, or just missing doing reviews. If you do want to tackle the review pile but feel too intimidated, you could try downloading a reorder script and working through your backlog level by level again, or by restricting them by SRS level. The script should help you have a more “normal” WK experience without needing to reset, though if you truly don’t remember most of the items from the last few levels, resetting back a few levels would be easier than trying to relearn dozens of items all at once.