A serious question deserves a serious answer.
My point is mostly that in many cases zooms are as appropriate as primes. I don't mean that zooms are superior to primes, just that good zooms at medium apertures are competitive with primes regarding quality. My other intention is to explain that you cannot simply just move instead of zoom, because moving changes perspective.
Now, much because I use zooms, I have an approach where I try to find a viewpoint first, than I find the focal length that gives the crop I want. I move around the tripod, sometimes as little as 15 cm just to find the right spot, this was the case at Oxbow Bend. I actually made a lot of images, at both 100 and 150 mm, and I was actually shooting two different cameras.
In the old time when I was shooting Pentax 67 I had fixed focals on the Pentax and zooms on Minolta, I was using both systems but at that time I was traveling by car. Now, when I am flying I cannot carry dual equipment.
I still use fixed focals. I have a Samyang 14/2.8, a Minolta 100/2.8 Macro, a Carl Zeiss Jena 50/4 in a tilting mount and also a Zeiss Macro Planar 120/4. Add to that 300/4 and 400/4.5, 20/2.8 and also a 50/1.4, but much of that may go into the trunk of the car. In the backpack I normally take three zooms and probably the Macro Planar 120/4 with its tilt mount.
How do you know? This is a serious question and I am not trying to be flippant. An 85mm and 135mm lenses would have made a different images, but no necessarily a worse image. Certainly a tighter crop could have worked with a 135mm. Not knowing what is outside the frame, it is hard to tell what the image would be with an 85mm. There is no such thing as the right focal length, only right solutions.
As far as perspective, there is also no such thing as the right perspective and how much does perspective change if you move a few feet with a landscape? And while the relationship of image size of elements in the image are fixed by the camera position, the apparent perspective does change with focal length. Some photographers do care about apparent perspective as it does change the perception of an image.