Each of them has had several examples of your "clunky dialog and wooden acting". First two seasons of TNG and DS9 are perfect examples. As with BSG, who says I was referring to the newer generation?
But even nuBSG has had problems itself, most of which is very subjective as to how much or how good/bad. For my taste, "Firefly" was one of the rarities when it comes to avoiding the "wooden acting". Since it lasted only 14 episodes, who's to say it wouldn't have had problems later down the line?
The point is that those symptoms are things most shows go through, particularly early on as the cast and crew get familiar with the stories and with each other. One thing that made B5 a little different was its use of a more stage-like presentation. That can affect a different perception as to quality, when there isn't as great a distinction. To be sure, B5's secondary actors were very "wooden" but then the show was on such a tight budget that it didn't surprise me at all. But I do feel their frontline performers compare very favorably with the best out there. True, they had a somewhat fitful start, but again... that's almost to be expected with just about any show.
The dialog at times was definitely clunky. Not much use in ignoring that. However, I never felt it was a distraction or all that frequent. I was so engrossed in the characters and overall story that minor annoyances were never anything more than that: minor annoyances.