I am in my fourth year of my PhD, a rather rocky journey which has involved my original supervisor being fired with little to no notice and various interruptions due to COVID.
I am working in the field of biological modelling, and both my former supervisor (an expert in the field but not very involved in my research) and my new supervisor (less of an expert, but very involved and a senior academic at my institution who has supervised dozens of students over multiple decades) are happy with my progress and never expressed any concern.
I have now tried a total of four submissions to different journals, and was always faced with a rejection. The latest, to an Elsevier journal, desk rejected after a few days. The previous rejected with rather disappointing feedback, lacking any substantial weakness or points where I could improve. (They even mentioned I didn't cite some key authors, of whom instead I had cited multiple papers...)
I am now worried I will reach the end of my PhD without publications, but especially without understanding what the core weaknesses of my work are. Even presenting my research at various symposiums nobody ever really raised any serious concern. My supervisor mentioned it might be because we are "outsiders" to the field, but that explanation doesn't fully convince me.