We still write up design review documents in Google Docs. A lot of the most important UX feedback we give in these reviews is on workflow, layout, and information architecture. The point-and-shoot nature of design feedback, not just in Figma but in all design tools, is more effective for visual design than UX.
I would propose something like a storyboard format. Once I have connected all the noodles of my prototype I would love to lay out the screens and state transitions in sequence, like a storyboard, with big comment fields for people to have meaningful conversations.
The tool also needs to be accessible to non-designers. PMs and Engineers remain uncomfortable in the guts of our tools, so it has to be presented in a familiar and non-technical format that invites feedback and contribution from other departments outside design.
One specific killer feature of G-docs is that when people comment and reply we get emails, further promoting productive conversation. This also needs to be effective.