Problem is they're really just toy characters. As long as kids want action figures and costumes there's no real desire from Disney to do any more than the minimum.
Which is a damn shame if it's the way it's gona be, because adding further depth to firmly-established characters is something everyone with a love for the source material - be it from a creative standpoint or just as a consumer of the stuff - can get behind.
Obviously there's a delicate balance to be found; a great deal of the
Star Wars audience would be pretty nonplussed if, say, Terrence Malick went Full Terrence Malick on these characters' stories, explicitly exploring their inner monologues and itching philosophical quandaries (I would dig it myself, but then I'm a bit weird when it comes to novel leftfield approaches to pop culture monoliths - I'd love to see auteur directors and highly idiosyncratic & cerebral writers and performers be given complete artistic freedom with comicbook heroes & villains & plotlines, and suchlike). But a property with such a broad viewership (the hardcore fanclub literally consists of anything from 5 year olds to 50 year olds!) should really be looking to engage both kids and adults pretty much at the same time - for the adults in ways other than just appealing to their inner kid. It should tell intimate tales in ways which reflect the inner worlds and life experiences of individuals both young and old who are watching, and it doesn't all have to be done with such broad brushstrokes, intellectual primary colours so to speak.
Loads of great modern works accomplish that feat, of entertaining the young'ns with riproaring fun and colour and adventure while also saying things which go completely over their heads but hit home hard with the old'ns, be it for worldly/near-the-knuckle comic effect, or emotional/philosophical/politically-relevant resonance.
The Simpsons mastered the art for a fair few seasons in its prime, and that was nigh on 20 years ago now. Many tele series, both animated and otherwise, have followed suit and built upon that all-encompassing attention to fine detail and overall quality, thus graciously bestowing upon them a rewatch factor that keeps on giving pretty much over an entire lifespan, not just by tickling the old nostalgia glands. Just imagine how well Anakin Skywalker's tale could've been told with that degree of finesse!! I suppose Lucas sort of went for
something like that, with the incessant trade agreement minutiae waffling and the like, but it was done in such an unwieldy and amateur way that it detracted from the work rather than augmented it. You know someone with real talent could've injected all that political intrigue, all the burgeoning romances both sexual and platonic, the brutal violence and betrayal and corruption and tragedy, and done it tastefully and efficiently, succinctly where required, with a real appreciation of the greater dramatic weight of certain elements and of the importance of smart feature film pacing.
Every new film is an opportunity to do it better, and for me that means going beyond a return to the style, structure, mirrored major plot points, etc. of the original trilogy. It means making good on the promise of ambitious epic storytelling that the prequels provided too, which failed in their shoddy execution rather than their initial conception. The appearance of matured characters should translate to a subtle undercurrent of mature themes, or else you're totally wasting an absolutely priceless aspect of such a long-running popular saga; that we have "grown up" with these characters, and they are older now too, just as we are. The immediate visual contrast and interpersonal dynamic with the new, youthful characters should be some real deep shit, what with us now having families of our own, mentees of our own, crushed dreams and painful losses and recalibrated perspectives on life of our own, and so on.
