Appreciate the KISS perspective.
For me, the project management features of a forge are extremely helpful. Setting milestones, assigning issues to them, defining timelines and regularly reiterating the planning has proven to accelerate our work as a team significantly. This experience refers to huge code bases (climate models) and medium to large team sizes, though. And probably also my bad memory 😵💫
I suppose it’s always good, though, to evaluate how much management a code will actually need in the end, and what tools correspond to that need.
Most ML development is done in Python to my knowledge. The reason is mostly the readily available side packages like torch, scikit-learn, etc. And Python, although not constructed as such, does indeed support a functional style. A quick search revealed a HowTo:
https://docs.python.org/3/howto/functional.html