That does look a very distinct line, even for a loop pile carpet that can be tricky to seam cleanly. The image is a bit small and I can't zoom in, personally I'd hope our fitters could achieve a better finish than that, however it can depend on the quality of the carpet and even how stiff the particular patch is. One thing that is for certain, seams will always be most visible on the first day of fitting and will bed in over the weeks and months.
Personally, I'd at least ask them back to take a look.