I think your take on it seems fine. The researchers did the poc, later it goes mainstream. The researcher should not care or be interested in the mainstream practical application anymore, they should be on to the next thing.
The research world, just like every other social circle, is full of people who are just parroting each other, repeating to each other what everyone already believes, and patting themselves on the back. Maybe, once in a while, one person takes a risk, gets a cool result, and then 100 others rehash the same idea with small variations. At some point, the field collectively decides what the next cool research meme is going to be, and everybody follows along.
So yeah, structural battery packs stopped being cool at some point, I guess. Except that battery tech 10 years ago wasn't the same as what we have today, so maybe the results don't directly transfer. The topic hasn't been studied in a contemporary context, maybe the old results are out of date, maybe they would really be worth investigating again... But who cares, that topic has been done, it isn't cool anymore, it was 10 years ago. All the cool kids are doing solid state batteries nowadays.
I'd be curious to know what your experience is that leads you to this opinion.
A more charitable explanation would be that game changing discoveries are by their nature rare, and even when they do arrive, they only outline a new space for exploration, which means that by definition, most research is going to be filling the gaps in that new space, both for positive results, and the depressingly large chunk of work that is discovering what doesn't work. The results of this negative outcome often look the same.