religion is a facet, or component of ideology.
But you can approach religions as a topic in countless ways, so I think it is fair not to reduce it to the lowest (albeit maybe most common...) approach people have
Religion has elements of ideology, some ideologies are derived from, related to, or specifically opposed to religious belief. That last might be an XOR.
In the non-jargon common sense of ideology ("a system of ideas and ideals, especially one that forms the basis of economic or political theory and policy", thanks dictionary) you're broadly right.
Like a dictionary? It's just semantics
If you remove all the cosmology and mysticism from Buddhism, you are left with something other than the original practice.