It is not uncommon to hear people complain about the state of certain legacy properties these days. The two most frequently mentioned are Star Trek and Star Wars but often entering into that discussion is the likes of Doctor Who or LOTR along with anything else that has lasted for decades when talks of reviving it get started.
There is no escaping that some validity exists in these comments. You can say such things have been said for years about (insert franchise name). Star Trek for example when TNG or DS9 came out had people get vocal but it was less about downturn and more if these new iterations could carry on the legacy. Now it is more about the weakness or general poor quality of offerings as they run. The Acolyte, which was a definitive nadir for a once culturally relevant property, got that treatment.

I have heard it said that the reason legacy properties are suffering these days is that they are being made by the people who grew up on them. They are not going to the well from which the ideas were drawn but going to the property and trying to mimic it. That is something I can certainly see and the more I think about it I think that’s probably a majority of the problem. Not the entire problem but a big one.
Star Trek TOS was birthed from the TV Western mixed with the growing social consciousness of the 60s along with a smidge of free love (see Captain Kirk). It was also a touch more. The writers understood the weakness of humanity. DC Fontana and the like also wrote character ideals we could look up to and strive to be like. They wanted to make a better society and teach moral lessons, but they always understood there were enduring human flaws that would not go away with good thoughts.
Star Wars was born of Flash Gordon and the hero’s journey found in all great stories and enduring mythology. Each film in the series was part of that and an individual example of that. All tinged with a struggle of ultimate good against ultimate evil. Today all the people see are spaceships and lightsabers.

If accurate, and I think it is, the problem is that the people behind the current franchises are trying to copy the distillations of the source material rather than pulling inspiration from the source or concepts that gave rise to a franchise. Star Trek no longer mixes together the Western with science-fiction and socially conscious messages. Star Wars has devolved into both sides often being terrible in their own way.
Such weakness is not harmful immediately but over time degrades the relevancy of a fictional world. While The Force Awakens was greeted with great excitement, Star Wars: The Mandalorian and Grogu has generated near indifference. While Discovery was born with some serious fanfare, its ending was met with thunderous apathy.
Then again most of these characters are not people you could look up to or would want to hang out with. While spending time with Sisko or Picard would be fascinating, an hour with Michael Burnham sounds like torture. Ahsoka would be great, but Osha or Mae would be like hanging out with the most vapid of a group of mean girls. Philippa Giorgio from the alternate universe in Star Trek: Discovery ate Kelpians but beyond that her on screen evil as they called it was just her being rude and a jerk most of the time. I can’t think of one truly dangerous thing that she did though I admit to stepping out on the show at the end of Season Two and only popping back in when the character got the Section 31 movie which was awful.

Without touching on the timeless themes and universal concepts that fueled so much of the franchises when they first began what you get is something that’s a pale imitation. It has the name and maybe some of the superficial aesthetics, but it has none of the deeper stuff that made them enduring.
Not that the studios are helping things any. Gone are the Jack L. Warners that at least had a feel for the common man or what made projects work. All too often they are run at best by café nerds who have an interest in some property, but not the passion and deep rooted knowledge. Perhaps they have a desire to make it reflective of them rather than of what it was. Some put in charge such as Alex Kurtzman may not have a genuine passion for what they’re handling but missed out on a job they would’ve preferred. Or even a dispassionate employee like Kathleen Kennedy. Kennedy may have been there every step of the way for many of the things she heads up now, but I don’t think she paid attention during the creative/creation process thus never achieving that special understanding.
All is not lost but changes need to be made. Maybe in some instances it is leadership but in others it is just in those crafting the product though neither action is likely.
