In Observable, a cell can define a function or return a value. When the value of a free variable within a function definition changes the function is redefined rather than the function being rerun. So there is a clear difference between points at which the function's bound variables come into play (function invocation) and the points when changes to the free variables have an effect (function definition). It's far from unmanageable in that "reactive notebook" setting. Maybe spreadsheets are the problem...

FWIW: https://www.nature.com/articles/d41586-021-01174-w