Yea this definitely makes sense for smaller monorepos. For us, we ended up writing our own dependency graph parser to figure out what tests to run (which is easy enough with a single language like python honestly)
We used pants initially (which I believe is similar to bazel). And indeed the dependency graphing it does was very helpful, but other parts of the tool motivated us to create something more bespoke and debuggable (we were only using like 20% or less of the features pants offers)