While this is annoying, I think we all have to accept that as a IL "daughter" or even "son" we are probably most interesting to our MIL/FIL as the parent of their grandkids.

So in some ways, this is par for the course. That said, why don't you weave in work issues/ stories as appropriate instead of waiting for them to bring it up? Of course you wouldn't want to rattle off a resume of accomplishments, but what about telling a funny story about a mishap or asking for advice (if relevant to the conversation) about dealing with a coworker. There may be "organic" ways of working in that side of your life into conversation and having them appreciate you as whole person instead of just spouse/mom.