Hey Ben -
First, I agree with the underlying idea that manual work and knowledge work are different. Therefore, I'm not suggesting using Taylor's methods wholesale without customizing it for knowledge work.
With that said...
#1
I think the idea that many of Taylor's principles can't be applied to creative tasks is wrong. Pixar, which is one of the most creatively successful companies of all time and was owned by Jobs, is extremely systematic about creativity and so is Apple.
Although the creative output might be different each time for a company like Pixar, there is always a process underneath everything that can be more systematic and can be improved upon.
Same thing for other meta-skills like communication, leadership, and decision-making.
#2
I agree that having the "one best way" for everyone probably wouldn't work in a lot of knowledge work contexts. But, I do think it is still beneficial to go through the process of finding the one best way for you. Also, I think it is worth companies spending more resources finding the best way to do things generally, training employees in those ways, and then letting the employees customize what works for them in their context rather than having the employee reinvent everything from scratch.
Cal Newport has a great article on the tension here in https://www.newyorker.com/culture/office-space/the-frustration-with-productivity-culture