Something that gives me hope is that I haven't seen anyone prioritize debuggability in a modern programming language or even a framework. Vale is maybe the first getting close: https://verdagon.dev/blog/perfect-replayability-prototyped.

I think there is a new era yet to come.

> probably too complex to visualize in a usable way

You can always abstract the complexity. A simplification of the control flow graph at the function level.

As an example, I want to understand the Postgres codebase better...there are a lot of very visualizable things going on there. If you look at lecture slides on relational DBMS, there are lots of diagrams...so why can't be view those animating diagrams as the code executes.

I was thinking of instrumenting the code to get a trace of every function call and its arguments, and then filter that and visualize it.

The key to this approach working though is a think ultimately we need to write our code and organize our code such that it can be easily visualizable. The purpose of code is for humans to understand it, otherwise we are writing assembly.