I think, ironically, they've tried to mix it up and not keep the exact same family/friend dynamics in order to avoid it getting stale.
Unless it's a cartoon, any show that has children featuring in it is always a ticking clock as they grow older, and it is going to evolve of necessity.
The Christmas special of Outnumbered last year really didn't hit the mark because the whole premise of it - young children doing crazy, unpredictable and embarrassing kid stuff - was now gone, with the kids now being adults. I used to love Outnumbered - I see upthread that not everybody did! - but it was always only going to work for a limited time.
Lee Mack has never made any secret of the fact that the sitcom context is purely a vehicle for his own stand-up one-liners. I've always loved it and I still do, even though there have been a few sub-par episodes in all of the time it's been on air.
Just going on the recently-finished series, for example, I thought the sex doll episode was quite grim, forced and not that funny at all; but I found the first episode, where they were viewing the house to buy, was top-drawer gloriously silly farce, and hilarious.