It cannot be changed, but in > 99 % of cases (rough estimation, YMMV) this is not an issue. For the majority of modules there is only one useful location or at least not too many possible steps up or down. E.g., all the raw stuff is at the very beginning of the pipeline, it would not make sense at the end.
However, one has too keep it in mind to find a useful workflow. One example: Whenever I watch tutorials for lightroom, people tend to use the white balance for colour grading. While I am doing this in dt as well, it is probably not the best you can do (in both programs). The white balance is early in the pipeline because it deals with the colour information from the bayer array and relates the colour channels to each other. Therefore, every change there will change the output of every other colour grading module later in the pipeline. It would be more straight forward to use the white balance to get a neutral picture and use other colour grading tools (late in the pipeline) to adjust the overall colour look.
For the cases where the fix pipeline is an issue, you could look into @harry_durgin’s workflow videos. The fix pipeline issue is one reason for him to save intermediate tiff files. But it is not the only reason, and I guess in most of his cases one could have found a way to go without the intermediate step. However, I hope there will some day be a functionality in darktable to automate the intermediate .tiff generation @harry_durgin uses¹, but it would be a convenience feature, and there may be other issues that have to be solved first.
¹To make it clear: What I think of is that you have still only one picture representation in lighttable, but you can have several chained pipelines and select on which to work. Darktable would then automatically work only on this particular pipeline and save the result as tiff in a cache or regenerate as necessary, which would serve as input to the subsequent pipelines. Only the last one would result in the final image.