Just an opinion: ideas do not come from nothing, so the larger the data pool (memories, experiences, interests) the more ideas are likely to be generated.
It very much seems like we live in an age of hyperspecialization; people know very much about relatively few things. Generally, these areas of knowledge are complimentary or related. Sometimes they overlap outright. Life is barely long enough to get good at one thing, so people often choose to specialize early and stay on one very fixed path.
From the outside looking in these collectives of experience are very tribal. They develop their own languages and symbols. They become these closed systems where ideas aren't created as much as they are simply refined; bounced back and forth among tribal members. But this does not seem to be a very good pattern for long term growth or sustainability. Homogenization leads to extinction.
What I mean by that can be understood by looking at the evolution of life on Earth as an example of the obverse. Evolution tends towards diversity. Diversity gives life its best possible chance of success. That way, when an asteroid slams into the planet, not everything dies. If evolution had tended towards homogenization (only making the best dinosaurs possible) instead of diversity, the K-T Event might have turned this planet into a floating rock.
It may be a bit of a weak analogy, but I feel like the same principles might apply fairly well to specific areas of knowledge. Ideas are the mutations that allow knowledge to change and evolve into something new. Exclusivity and specialization are a sort of homogenization that leads to stagnation and fewer truly new & good ideas. Not that ideas don't happen at all, just that maybe they happen less often than they should... or could. I don't know, really. This is mostly just speculation based on personal observation and opinion.
Colloquially, I can say that the people I have known in my life who seem to have the most ideas are the ones whose interests are all over the map, so to speak. They tend to be older, with a deeper well of experience to draw from. Their knowledge pools, being varied as opposed to complimentary, allow them to look outside these otherwise closed systems and make inferences, or to see patterns that people too mired within the subject matter might easily miss.
They may not always be good ideas, but they are often striking in their seeming originality and unexpectedness.
An example that comes to mind is of a family friend who worked for years in automotive manufacturing before going back to school to get his certification as a laboratory technician. He got a job as a lab assistant at a University research hospital. He would overhear the researchers in the break room talking about their current projects, and one of them that really grabbed his interest was the problem of infectious disease control measures, specifically, getting healthcare professionals to wash their hands between patient interactions. He had the idea, based on his experience in manufacturing, to apply Poka Yoke (a Japanese manufacturing term that roughly means error-proofing) to the problem of getting nurses and doctors to wash their hands between patient encounters. His idea was to install sink-locks at all the doors to patient rooms. These doors would only open from the outside if the sink was used for at least 20 seconds immediately prior to opening them, or if an emergency button was pushed. From the inside they open at will. He mentioned the idea in casual conversation with one of the senior researchers who was so excited by it that he wanted to design a study around the concept.
I feel like there is a potential benefit to be had by looking outside as opposed to focusing too intently within. Maybe spending some percentage of time learning about completely new things as opposed to only endeavoring to learn new details about things we already know might yield an increase in new ideas. There's nothing wrong with getting out of our comfort zone and challenging our perspectives.
This reminds me of how little control you have over your own mind. However, that is not the worst part. The worst part is when you don't realize how little control you actually have.
I think I have almost my entire life fallen prey to the fallacy of believing that emotions don't affect me. I thought I was impenetrable to feedback on the emotional level. That I could, with a cold mind, extract all of the object-level information from feedback. But then somebody gave me very negative feedback on an article I had worked very hard on for over a week. Afterwards, I basically stopped writing for 6 months about that topic. Actually, I think it still affects me now, 1 year later.
I think all of this would have been a lot less terrible had I realized what was going on. I did not even consider the possibility that I was not writing because I got some very strong negative feedback until maybe 4 months ago.
I think there is probably a time and place for intellectually isolating yourself if you are prone to this failure mode. I only notice now that I have often intellectually isolated myself in the past, and that at those times I never ran into the issue of not being able to come up with ideas. However, I think feedback can be extremely valuable, so there is certainly a balance to strike here.
That was potentially valuable early on for me when I started to write down my ideas. I wrote down probably over a million words worth of ideas before I ever wrote up anything publically. I am pretty sure >3% of all the writing I have done is public right now.
Now that I frequently talk to people about the things I am thinking about I am constantly running into the issue that I get critique about something other than the thing I am trying to explain because I am so bad at explaining. Often this only becomes apparent in hindsight. I think this could have been very damaging early on if I always got this kind of negative feedback. However, it's worth noting that not isolating myself for so long would probably also have helped me get better at explaining.
Becoming good at detaching yourself from your ideas is probably better than isolating yourself as much as I did.