Consider the exchange between the Enterprise and the Romulan commanders for a second. Both sides agree to form an alliance in figuring out who destroyed their outposts. 10 seconds later the Romulans randomly decide to break it off for no reason other than to tell Picard to shove off.
This exchange really felt like one of those instances where there was supposed to be more going on, but Maurice Hurley had to rush it because he wanted more scenes with our one episode only characters who will have zero relevance as the series progressed.
Sometimes I wonder if instead of three 20th century humans that were picked up it would be three Romulans who were rescued. Without the Romulans telling the crew anything about what transpired at their outposts and them being unsure if it was the Federation that did it since they were rescued by Starfleet's most advanced vessel. And for the Enterprise crew to be suspicious of them in wondering if they had anything to do with the destruction of their outposts.
Also, had there been no 20th century human characters, we would have been spared those preachy "Humanity has evolved!" and insulting "It's a wonder how we even survived as a species" moments.