Scala 2 is a dying language, and Scala 3 is an immature one. The ecosystem and community are also very messy, with fragmentation and witch hunts running rampant. OCaml provides same advantages, but without all the drama.
> I wonder if this will wind up being a category of problems and the solution is a separate "system" set of effects (effectively `({user}, {system})`) or if this one-off extension is all that will be needed.
It already is, kinda. In my practice very often you have global singleton values that are either defined as static variables, or passed as arguments to nearly all functions in a module. Since implicit presence of `Debug` effect is already a compilation parameter, it could be generalized to support any sets of implicit effects. Thus you might design a module that has implicit Logger and Database effects in all its functions.