If you still do the sizing (it’s not entirely wasted as it’s a reasonably effective tool to gauge understanding across the team), This can still be done without the artificial time boxing.

“How much work have we done in the last two weeks?” Just look at all the stories closed in the last two weeks. Easy.

“When will X be delivered?” Look at X and all its dependencies, add up all the points, and guesstimate the time equivalence.

Kanban isn’t a free for all, you still need structure and some planning. But you take most of that away from the do-ers and let them do what they do best… do.