I star projects that have caught my attention and might be relevant for my work, or that I will need to reference later. I don't see how this relates to a display of gratitude.
Star too, donate too, whatever you'd like to do normally too but nothing beats actually using your words
Github launched Github Sponsors in 2019. It does basically everything you described aside from the "thanks" part.
"No I said don't do th.. ah forget it"
Unstar however would become “No thanks”