How do you help a prospect evolve their thinking about a business process when they have 20 years work experience with the legacy incumbent that they don’t love, but it’s what they know and built their processes around?

Interesting one. On the one hand side change is the only constant, but no one likes changes because it means uncertainty.

Therefore try to replace the fear of uncertainty with the desire to create something new, something better (with your product). Build up a story on where they will be like in 1-2 years with your products instead of sticking to the existing one. Make them want this future and explain why only you can build this future.