Kinopio is for a very particular type of thinking in public.
mmm.page is for making websites, alongside a couple other similar tools.
tldraw is for quick diagrams and rough sketches. Excalidraw is similar, but offers more customisation.
Scrintal, Heptabase, Nodebook, etc. are all trying to be knowledge management tools.
SCRAPPLE will be digital paper. Shareable when required, collaborative when desired, and as much of an offline-first app as feasible.