I agree that television audiences were concentrated into a smaller number of channels, but I don't agree with using that to frame any-old-show-of-your-choosing with this idea that it was only tolerated/justified because of the fact. Mass appeal is mass appeal, and that still rules the roost in the world of mainstream broadcasting, so I just view most attempts to 'explain' a perceived undiscerning past with it as present-day vanity.
Mrs Turnstyle: Can you help me take the Christmas decorations down?
Me: NO! I'm too busy arguing with someone on the internet about the perceived mass popularity of Keeping up Appearances!
Mrs Turnstyle: That old sitcom with the posh woman?
Me: Yes! Well, she wasn't really posh, it was more a front to try and elevate herself to a higher social status.
Mrs Turnstyle: But...why?
Me: Because in a lot of older British comedy, class and the desire to move up the social ladder was a central component. Think about it. Steptoe and Son, Only Fools and Horses, Fawlty Towers...
Mrs Turnstyle: No, I mean why are you arguing with someone about Keeping up Appearances on the internet?
Me: Because I've lost control of my life.