Unfortunately, I have noticed this phenomena as well. You have all raised good points on the subject that are not incorrect. I also believe that there is a correlation with the growing illiteracy amongst today's youth. Kids today probably won't be as interested in a LEGO story told in long form as a opposed to something like a short comic or meme. Although I think there is still potentially a reasonably sized audience for LEGO stories.
Personally, I think one of the main reasons for the big decline over the last few years is due to poor execution on the part of the writers (no offence to anyone here, if we're gonna play the blame game I'm as guilty as anyone). First off, there's a critical lack of marketing to promote these stories around the internet, so most of the potential audience is left in the dark. Secondly, there hasn't been a major blockbuster epic like Ikros, since Ikros (which was over ten years ago) so many people even within the community don't realise the potential for LEGO based stories. Back in the day, I read a couple LEGO stories with vague interest but wasn't really converted until I stumbled upon Ikros. There have certainly been a few really good stories since then (many posted here) but none have or have yet to fill the the void left by Ikros.
I live adjacent to a comic book store, so I have some idea of what is going on in the industry. Its declined a lot in recent years, but it still has a core fanbase that keeps it going.
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