It is super frustrating thinking that you are loosing skill or lost a lot of your progress especially because this is not really true (the muscle-memory still exists) :
The hardest part might be to get past this mindset. Try thinking about the very beginning of your ctb journey - a typical player should be proud here to fc 2* maps and find it near impossible to read AR8+. Thinking further about how long it took you to reach certain personal milestones like the first passed 3*, 4* map or the first catched hyperdash and this should make you realize that it is not all gone at all. The best thing is that once you've learned something like ever, you'll relearn it much much faster this time, too.
Consider playing a bit differently than before until you regain your abilities.
Like try playing a new mode like HD or DT so you are guaranteed to make progress there since you are starting at 0 in this category. Like thinking about no matter how bad you are there, it is still a new pb. (or, if you run out of modes, create own challenges like catching most bananas, only using the left half of your plate, catching every fruit in the very center, no-dashing low diffs,...). Or play different maps. Play lower or higher diffs. (I usually play easy but loooong maps first, this gets me bored so I am hyped to play super hard maps afterwards). Also, it is a GREAT opportunity to play multiplayer. This is all so that you have no chance to compare yourself to your previous best form.
The short answer is that you'll eventually get past this and it probably happens faster than you think it will.