You're all overthinking things way too much.
The vast majority of people like what they like, and dislike what they dislike, because of influence of their peers and society. They see people who get attention and want to be like them. It's the same for astronauts or movie stars in previous generations. Whether they realize it or not, children pay attention to the people they see to notice what is encouraged, and they naturally gravitate towards that. The media itself is largely irrelevant- print, TV, blogs, video, whatever. It's just part of our natural instinct to 'belong.' People usually think they like those things because they just like them. But they like them because in their life, it those actions have been associated with positive dopamine feedback. It's really as simple as that. Well, unless there are other factors like autism involved. But those are the exception to the rule.
So, unless there is some big government or media push for a new space program glorifying astronauts again, there will be a lower interest. Musk has a chance to really turn things around though, but that's about it. Another factor is how often things happen. With space, it can be years between big events to look forward to. Those dopamine hits are larger, but they don't happen that often. There is also a limit to dopamine hits. Online media like twitter and Instagram have continued to maximize their platforms for this. Instead of waiting weeks or months for big events, these artificial ones happen all the time. Dopamine is a huge motivating factor, and kids nowadays are absolutely flooded with it.
So nobody is talking about it, so it isn't reinforced. Either the government or big celebrities would have to push it for quite a while to change things- it doesn't change overnight.
To add...
It's the media companies and our current profit models that are really driving it. Social media is driven by ad revenue, which is now driven by interest. Clickbait and fake hysteria are big business. The rest f the problems stem from this feedback system. It's really quite an unfortunate situation.