Right. The Making of Star Trek said outright that the Klingons despised honor and celebrated treachery, while the Romulans were the noble and honorable ones. That started to get switched in TSFS when they wrote the script for Romulans and then basically crossed it out and wrote "Klingons" in its place, so suddenly Klingons had cloaked Birds-of-Prey and talked about honor.
But that's revisionist nonsense. TOS/TAS had five episodes with Romulans at least theoretically in them. In
all of those, the Romulans despised honor and celebrated treachery.
1) "Balance of Terror" has subordinates working behind the backs of superiors, and superiors conspiring to defeat the aims of their leaders, all as part of a surprise first strike with an invisible ship so that a war can be launched against a party that has not lifted a finger for a century.
2) "Deadly Years" has Romulans ambushing a mission of mercy in the RNZ, a region they have no business being in, and refusing to grant as much as a cease-fire for a victim that apparently never fires back.
3) "
Enterprise Incident" has a Romulan maneuvering for personal glory and thus jeopardizing a mission; drinking with the enemy, and trying to make the enemy defect; and then basically defecting herself.
4) "Survivor" has Romulans ambushing a starship they lured into the RNZ, by blackmailing a bystander into being an operative.
5) "Practical Joker" has Romulans ambushing a starship outside not just their own territory but outside the RNZ as well, under disingenuous claims to the contrary.
On the other hand, the Romulans gain no honor in later writing, either. They simply happen to be generic villains who have evil in their blood, and are written as such across the board - even if they belatedly gain the nuance of being cousins to Vulcans, a factoid that went dramatically unused for decades originally.
He's not weary of duty per se, but of the fact that his duty forces him to follow the orders of a dishonorable, warmongering Praetor.
...Orders he then cleverly subverts, by committing suicide where there is no need for one, thus turning a mission of great success into a deliberate disaster. But that's high treason, and the "high" part doesn't indicate exalted ideals, either, except from the viewpoint of the enemy of the Romulans, the one this guy supposedly swore to defend the realm against.
It's downhill for the Romulans after that, with no redeeming aspects to their conduct. So I can't accept that anything ever "flipped". What happened instead was that the Klingons were utilized more, thus necessarily gaining in features, one of which happened to be obsession with personal glory. And that's about as generic as you can get with a villain: "I'm baaaaad, badder than anybody else!"...
Timo Saloniemi