Sounds tight! I have a C# .NET Core ML implementation but I had to write it from scratch. It suits my needs but the Python ecosystem definitely has more to offer in terms of ML libraries.
The fundamental difference is real support for tuples/vectors and operations on them. Many of the operations have direct counterparts in CPU/GPU and do not have parallel in C#. I don't know why anyone would do anything ML in anything other than python. 1. In order to get proficient in ML, one had to go through a gazillion of python examples. It would take a deliberate effort not to learn it. 2. Just complete lack of anything remotely matching python ecosystem. A glaring example would be a Light GBM. Microsoft-developed ML library that does NOT have C# interface. 3. Subject matter at hand (building ML-based trading sys) is complicated enough, why make it any more difficult with exotic tools that WILL have spotty support.
Python was not the right tool for what I needed. I had specific requirements and .NET Core worked perfectly.