You may start to get a point when C# gets a two-directional type inference system. As it's now, any functional-looking code requires so much boiler plate that it's shorter and less bug-prone to copy your functions code everywhere you want to use them.
Can you give an example of said boiler plate?
Just try to make any generic high order function in C#. Any one you can think of.
Using OneOf library or something similar instead of discriminated unions / sum types.
Trying to use a functional pipeline instead of DI.