Hi I am fairly new to Lucid but have extensive 10 years + experience with draw.io. Let me make some observations:
1. Allow the user to select part of a diagram and then print should be able to determine you have selected part of the diagram and print just that rather than have to crop
2. Improve your shapes !! This is one of the worst aspects if I search for something I should find what I am looking for. If you need inspiration then go to draw.io
3. Large text boxes far bigger than the size of the text - causes massive issues when it comes to selecting objects within objects. Incredibly frustrating
4. Dont allow the Standard shapes to be closed I mean why would anybody even do that ?
5. Large diagrams draw.io copes with large diagrams seemlessly unfortunatley lucid does not I can't share the diagram due to privacy however it is true to say lucid is not performant