What's missing in these is cross-reference, which is not possible without somewhat established BUILD system (caps "pun-intened") - e.g. like bazel/build, then a source code indexer, etc, etc.

This becomes very critical for doing reviews, since it allows you to "trace" things without running them, apart from many other things. For example large scale refactorings looking for usages of functions, and other examples like it.

Why githab/gitlab/etc. can't do it? Well because hardly there could be one encompassing BUILD system to generate correctly this index.