Even within many of the stand-alone episodes, there was a lot of character/relationship growth, conflict and development, I believe more so than other shows partly because most of the DS9 characters were flawed as the author says (much more eloquently than I could). And while the specifics of what happened within many of those episodes weren't part of the broader story, there were layers of recurring aliens, cultures and politics that needed some exposition and development, often as "stand alone" episodes. Plus as the series went on, more and more characters were added to the mix to explore and develop. So for me, all of that was part of the serial or the "epic feeling" even when some of those developments occurred within stand-alone episodes.
I would say you're right, except for the part about that being present in Deep Space Nine more so than the other series.
You can find all kinds of examples of this kind of continuity and world-building in TNG. The fictional worlds of DS9 and Voyager were literally built in TNG with episodes like The Wounded, Ensign Ro, Chain of Command, Lower Decks, Journey's End, Pre-emptive Strike... You may not be as interested in the themes and characters being developed on TNG as you are with the ones on DS9, but they're still there.
The article is trying to say that DS9 was a serialized TV show in opposition to TNG consisting of solely one-off stories, and that because of that people cruelly misjudged it, leaving it scorned in obscurity.
In reality, DS9 had great ratings with wide exposure, and the only times DS9 became more serialized than TNG was the 3 part season 2 opener, the 6 part season 6 opener, and the 10 part season 7 closer. That is 19 out of 176 episodes.
I agree that DS9 was not 'too complex' for the average viewer, but I disagree that the reason not as many liked it has to do with quality.
It has to do with the way most people watch TV. Most people just want a fun escapist adventure, they don't want dark characters exploring the moral ambiguities of war and religion. DS9 doesn't give people what most people look for in a TV show. But that has to do with breadth of appeal, not quality.
Again, I never said it has anything to do with quality. Clearly DS9 was made with same level of care and craftsmanship as TNG, some could even argue that it surpasses it. What I said was that it simply didn't interest some of the audience of TNG. It was given a fair shake. The ratings for the DS9 pilot were massive. A whole bunch of people gave it a shot, and then a portion of them said "no thanks." It doesn't mean they were unable to comprehend deep dark characters or whatever elitist sentiment gets tossed around. They weren't into it. I am. That doesn't mean I'm able to see something they don't, it just means I like what I see and they don't.