Not really in the begining. Drew Deighan wrong "SOTF." Ronald D. Moore and W. Reed Moran were the teleplayists but I think Moran had more to do with that episode.
"Reunion" was not written by Ronald D. Moore.

LMAO. I sense a passive disrespect towards him. Like they were putting up with him. I can't stand Ronald Moore. He's codeless and loves
Basic Instinct
and
Xena
. I say this because he proudly was part of
Battlestar Galatica
which could have been another great
Star Wars
-like show the way
DS9
, but Lucy Lawless had to be on it rolls eyes. I don't even hate his criticism of
Voyager
, although I disagree that they were a weak show. I just that **** about him.

RDM wrote mostly just the Klingon episodes, and was known on staff as "The Klingon Guy"
I've always been wired for unfiltered truth, no matter who it offends.

The post-Borg episodes still had a sense of threat that the Borg could be invading Federation, Cardassian, Romulan, Klingon space anytime. But it was really the advancedness of the Cardassians that really posed the biggest danger to the Federation. And yes they were more advanced (even the events of "The Wounded" are a case of you can't jump to conclusions, and Macet's ship was a cruiser, rather than a battle ship; later on Picard seems cautious about a confrontation with two Galors). Even episodes which were not about them before "Chain of Command" had them referenced in a threatening light ("The Mind's Eye" makes them out to be a major power in the galaxy, and "Realm of Fear" raises the possibly of a new Cardassian front, and that did eventually happen episodes later in "Chain of Command"). Which adds to the Berman/McCarthy/Chattaway handbook.
The dooming tone ended when
First Contact
came out and the Borg became the pussies, which
Voyager
further weakened. But there still were some threatening episodes with the Chattaway tone ("Scientific Method", "Inferno's Light").

Well I don't know if I can give him purely the credit. That might be more Rick Berman than him. His dominance seems to come when Dennis McCarthy/Jay Chattaway started becoming the regular composers (I believe "The Drumhead" was the last Ron Jones episode). The show took a more starker turn from that point on. And I believe after season 5, Gene Rodenberry doesn't appear as executive producer.

I think some of the episodes from the first season were old unused Star Trek episodes or episodes for an aborted series that Roddenberry did have involvement in so at least for the first season he has some responsibility for the optimistic tone. Ronald Moore might have added a more martial instinct to the series.