People (me included) say this every year!
But the producers are showing us a gameshow, not a reality show, and are going with what the target audience responds to.
DD is squarely the target audience and has been watching avidly in last couple of years - and is the reason I watch as we do it together - plus she also has watched some earlier series on catch-up.
But she's a bit fed up with it atm, and In suspect she's drifting away
And that's probably their model - keep reeling in young viewers, engage them with online content and get them watching a show which is attracting large advertising revenue (watching live, hooked by narrow voting window at end of a show with a slightly variable end time). With aim of keeping them for 2-3 series, but no expectation of longer