No, you are definitely not alone.
I met my now DH when the DSC were similar age to yours, and we have a DD now. There are things I find really hard to understand about the choices DH and his first wife made with regard to the kids, and it did worry me that I'd be continually struggling to raise our own DD more in line with my own values and ideas.
DH did not have strong views, though - I mean that - according to him - it was not so much conscious parenting choices on his part with the DSCs so much as a lack of foresight or a sort of inertia. One of the kids was quite strong-willed even as a child, and it seems they just sort of gave in to it and gave her whatever they had to to keep her 'happy'. We don't have a clash of 'parenting philosophies' IYSWIM, because he says that he never had a 'parenting philosophy', just did whatever got them through the moment!
He was very open to doing things differently, and has been happy for me to take the lead with DD. Because of the large age gap - and I hope you will find this too - it is actually not that difficult to do things very differently. We can have different rules and expectations of DD, and do different sorts of activities, because of that age gap. Sometimes DSD gives me grief by talking about how things were so much better for her...An example - she was allowed to draw on the walls and furniture because in her words 'mum and dad thought it was important for me to express my creativity"; in DH's version, he hated that but didn't seem able to stop it and mum didn't mind it) - the not so hidden message is that I am stomping out DD's creative spirit, but I can laugh at that and carry on! The DSC had a lot more material things and expensive experiences/activities than I either can or wish to provide for DD, but again, the age gap means I can pretty much laugh it off. And I think it is good for the DSC to see us/their dad doing things in a different way and seeing that it works.
One thing that we did with the older kids was to sort of 'take turns'...you could choose an activity one time, and let each of them choose on their turn. That way no one feels criticised so much as they feel they can share something they enjoy.