OP I do know how you feel. My DS's CC has a 'primary carer' model, and in his 6 terms at CC he has had 5 primary carers.
When his latest one arrived, I did say to her that I'm not sure that the Primary Carer model is the best approach at this CC with so many regular changes. I feel that my son was disadvantaged (or unlucky) when other children were unaffected with so many changes, and it's fortunate that he has adapted so easily to a range of carers. I also gave this feedback to the centre in our parent survey last year.
I realise that staff turnover (and one was maternity leave) is somewhat hard to predict, and I wasn't making a complaint as such, but it just seemed that they needed to rethink their philosophy to allow for staff turnover.
I think feedback is important and as parents we have every right to advocate for our children.
Having said all that, and being a teacher myself, I do think that it's just the way the world works. Childcare workers have no less right to make decisions for their own family/happiness/wellbeing, and in all reality they don't owe us anything beyond doing their job well while they are there.