Having used Multics and a farrago of other OSes (not CTSS or the Berkeley timesharing system) as part of my retrocomputing hobby, I think the single biggest thing Unix brought to the day-to-day experience of using an OS was the pipe, and the concomitant transformation of the command line from just being a way to enter program names with command line options (on OSes which even have command line options as we know them, of course) to being a programming language in its own right suitable for rapid prototyping and the creation of glue code.

Glue code isn't glamorous. It isn't something which seems to get a lot of research put into it. It is, however, important to get right, and part of getting it right is foregrounding the right thing: The stuff you're gluing together, as opposed to the glue itself. This is something the "replace shell with a Real Programming Language" projects get wrong, in that the Unix shell defaults to treating unknown barewords as external programs as opposed to syntax errors. This plays Hell with any kind of automated analysis, but it's essential for a language primarily intended to glue those external programs together. Typing isn't just about the type system, after all.

TL;DR: OSes prior to Unix had surprisingly weak scripting facilities, and attempts to "improve" scripting tend to miss the point.