My group submitted a paper with journal A and it spend a really long time in review, the editor seemingly had a lot of trouble finding suitable reviewers. There was a revision about half a year ago. In the mean time, our research on the project has processed and newer results along similar lines have been submitted to other conferences B and C.
Now journal A got a new review in (more than a year after original submission), which recommends a major revision and criticizes insufficient novelty. We have improved results since then but those are already submitted to B and C. We don't know yet if B and C will accept and the revision is due before we will know. I understand that it would be very bad to revise it such that there are overlaps and end up with multiple publications with similar results but if B and C are not accepted, that concern would be moot.
Asking for more time to revise to know whether B and C will accept and make a decision based on that would be dishonest. I am concerned that retracting the original submission will make the journal feel like we wasted their time and used their feedback for publications elsewhere. I am concerned that asking for an extension to wait for the decisions of B and C will look we are wasting everyone's time to then pick and chose. With the benefit of hindsight and later results, I am not a big fan of manuscript A anymore but I am concerned about reputational damage for my colleagues and me and I also understand that the editor had to send out a lot of emails to get the few reviews he got over that long time.