Oti is a fab choreographer and teacher. I know she's not everyone's cup of tea, but she does have that knack of getting the best out of her partners. As much as I'll miss her, it does feel like the right time for her to leave as she can't really do much else (apart from win the Christmas special with Danny Mac ha).
Interesting that she chose to put it out there now, months before the series has even started - maybe so there won't be endless speculation about it during the series.
I'm not a fan of her OTT competitiveness and screaming, but I think Amy's choreography is good in that it always seems to be geared towards her making her partner shine rather than her showing off. Katya can be a bit hit a miss for me, but I do hope she gets a ringer this year just so she can go all out with it.
But yes, without Oti, choreography is a bit lacking overall. Apart from Gorka and Giovanni, I don't think any of the male pros are that great at it either.