Humans are more complex than sequential narrative yet narrative makes them easier to understand. We encourage others to build their own narratives so that we can understand what they want us to understand better and can thereby avoid the complex layers of the human condition that are non-linear.
A narrative is a resume and it is often useful in society to build one for society’s sake and sometimes useful to you if you need it for a grounding of “who am i?” after which you can tell yourself a tale of yourself and find comfort in a logical progression from then to now and perhaps a pathway to your future in the form of purpose or at least of a core from which one comes forth from out of.
Yet I wouldn’t say it is an illusion. It may be the best one can grasp onto. I can’t say if there is something more fundamental than having a grounding. To say there’s “no grounding” isn’t a foundation although it can give you permission to built one yourself if you like or not.