So this is very loosely inspired by a theory I have about Star Wars as a setting, but it is not something they really discuss overtly even in the Extended Universe. One of the interesting things about the setting is the fact that there really doesn't seem to be much in the way of technological progress. The only reason this could be the case for this long is if they have essentially discovered all of science. Everything from genetic engineering of behavioral traits to a theory of physics that incorporates something as unusual as hyperspace has already been done. Any technology we don't see must be a consequence of something else, like the metaphysics of The Force preventing the development of Trek style transporters and transhumanism or extreme insecurities leading to a lack of networked computers.
What is interesting here is that any scientist would be either an engineer, who is applying principles that are already well understood, or an archaeologist, digging into things from the past lost to time.
Engineering(and similar fields like medicine) is all about applying science that is already fairly well understood, with the focus on different types of tradeoffs. In the Star Wars example, one starfighter isn’t more advanced than another, it is simply a case of trading speed for survivability for cost. The Empire wants cheap and agile fighters while the Rebel Alliance wants durable ones that are useful against capital ships.
Because the setting is so old an, past technology can still be competitive with that of the present. When this is combined with the age of the setting, it means that the only field of science that really has anything new to say is archaeology, because history has so often been lost to time in this context. What is nice about this angle is that history is generally more easily understood than a real scientific field, which makes it easier to come up with alternative theories that are something other than pure technobabble. It is much easier to think about causal connections in history and how those can be altered by new discoveries than it is to think about entirely fictional physics and metaphysics.
AI/droids is also a factor here, in which they handle much of the technical work as well. We don’t really see human doctors all that much, with medical droids doing the overwhelming majority of the work. The same is likely at least partially true for engineers and archaeologists. There is probably a droid that does most of the calculations or digging.
Does this seem plausible enough as part of the basis for a new setting? How long would you need this level of development for this to be plausible?