There's no accounting for tastes of course ... but I would give a opposite review to the one you've just read. I don't live in Spain so I don't know what the Spanish think of this show, but to me it fills a big question mark in my mind. I grew up studying Spanish and all through highschool, college, and graduate school I heard stories of Spain under Franco, but didn't really understand what it was like. "Cuéntame", as the other review mentioned, is set in the last decade of Franco's rule. If it's accurate, this show gives the "taste" of a very particular and very important period that has a lot to do with the way Spain is now (even though there is in many ways very little resemblance).
The show can be a little too earnest sometimes, and sometimes it's obvious that they are trying to touch (even though lightly) on all the major issues of the day and come out on the right side in each of them. But I think there is also an interesting balance between the outrage of the kids who are just realising what's going on in their society and the parents & grandmother who have seen it all and are cautious about getting involved in politics. And lots of arguing about things that matter, the kind of getting-things-out-in-the-open that I would expect from the Spanish families I know. Not a kind of arguing that tears families apart, but one that is a natural part of living together and getting to understand what makes the other person tick. And even if you never understand them, they're still Family. That's the other nice part of this show, apart from the "historical" value: there's lots of qualities in the Alcántara family that reminds you of the best in Spanish family life.