What do you mean? If you run pip freeze inside a venv it will print every user-installed module and their dependencies. When installing them in a new venv as a requirements file, you end up with the exact same set of modules.
Agree. Works fine for me exactly as you describe. I don't understand why people furiously want more than this for the common case. (Choose python version, create .venv/ directory, install packages, use installed .venv/ and do work.)
Sometimes it works, sometimes it doesn't. This is indeed a problem, but one for which there isn't an elegant solution.
When multiple versions of the same library are allowed to coexist in different dependency trees there is less incentive to solve these conflicts and versions proliferate (see npm).
I'd much rather solve the occasional conflict (usually solved either by settling on some older version of both parent dependencies - and later advancing as possible - or just trying to fix it and send a patch upstream).
Issues start occurring when you, for example, delete dependencies because with pip freeze you cannot ensure that you have deleted their dependencies also. The most common solution to this (that poetry and pipenv use) is to provide a lockfile to track transitive dependencies and their versions, without that (except for manually curating your dependencies) you can't ensure that you get a reproducible environment.
OK, but it does manage the versions of transitive dependencies, and there's nothing in that process stopping deterministic builds.
Adding/removing top level dependencies over time does require the use of two files (the top level requirements and the frozen/locked requirements which lists everything). Or you can list the top level requirements in setup.py and let requirements.txt be the lockfile. It would be nice if pip managed this lockfile automatically, but I'm not really interested in adding any of these newer tools to my toolchain just to manage a lockfile.
There are many packaging and distribution frustrations in Python, I don't think pip's management of dependency lists is one of them
