My experience says that this is not always true.
Especially in companies where a lot of people are involved in designing, developing and maintaining deliverables.
The communication between designers and designers (eg UX and UI), designers and stakeholders and designers and third parties is crucial for increasing the speed and the quality of the shipped deliverables.
Finding the right tools to use can be a serious boost to the process.
I worked a lot with Fireworks due to the combo between vector and raster and the low learning curve because most of us were coming from Illustrator.
We decided to switch to Sketch 2 years ago and was a huge investment in terms of time and effort to make the old deliverables available within the new set-up.
Now we are very happy with it because of the huge amount of plug-ins and the high compatibility with InVision.
With the new feature to prepare the clickable prototypes directly in Sketch we can make the full process even faster.
I'm not saying that Sketch is the final weapon for delivering UI/UX but, it's a matter fo fact, is one of the most responsive tools for each phase of the product design process.