If Affinity really cares about the creatives, they (& all other design companies, hopefully Adobe too?) should have form a group to create a file format standard. As long as the design format is proprietary, there's not much "freedom" here, even if the software is free, paid-once or subscription-based.
Sketch is actually almost there, at least for UI/vector designs (https://developer.sketch.com/file-format/), but designers end up moving to other tools like Figma, etc.
