Yes, a lot of the 'issues-led' drama was pretty preachy and lecturing by today's standards. I caught one a while back, which I think was a Ken Loach thing. It was about a man from a very working class background coming back from the trenches in WW1 and not accepting the class system. He ended up in court, and gave a speech about injustice from the dock. The sentiments were laudable, but the grammar, sentence structure, logical argument and so on were not remotely in character for someone who would have left school at 12 or so. It really jarred. I think a lot of the 60s and 70s dramas were a bit like that. Kitchen sink drama was definitely realistic (ie the settings and plots were like real life) but not naturalistic (ie the dialogue wasn't a good fit).
Even in the 80s, Brookside slipped into sociology classes at times. Bobby Grant talking about the unions and Paul Collins arguing the managers' case were real set pieces.