The todo-list as an outcome will sometimes be very short, yes. Then again, it is a list people have volunteered to commit to and the odds of those actions getting done are more realistic. Otherwise, you might get many actions, but if the most actions on it never get done, it was an unrealistic list after all.

My 2 cents

In your post, I can follow you with the reasons you provide for your change. It’s always a great danger, that Retrospective meetings suffering from repeating equability (“Groundhog Day” – effect) Changing things can be a fresh weak up.

On the other hand I would be scared to limit improvements to improvements some one would volunteer for solving it. Many issues and necessary improvements need to be solved by the organization itself, by the management or other departments and they are thus a natural part on the Scrum Master’s impediment list. I’d guess, your final todo-list as outcome of the Retro might be very short?

On the other side, the manage by results. If the whatever-to-be changed is just on a list then it may well not be a commit. The ”failure” to take things on is addressed in software Kanban by mgmt limiting work in progress and monitoring that the work gets done.