> It looks off

Depends on what you want to achieve with your look. Do you want to scream professionalism, authority, and completed? Use a regular UML tool.

Want to say this is a rough draft of a few ideas? Then using UML is probably THE wrong look. And Exaclidraw should be used instead.

--- Anecdote time. According to one of my professors, they showed how the prototype will look in action, and the customers were so impressed by the smoke and mirrors prototype they wanted to start using it right away.

In the end, customer walked away because they thought they were being strung along to pay for something that was already done.