I explained that – or I tried to, anyway. 
The earlier soap era used the umbrella format to ensure a variety of linked storylines were going on at any one time, spotlighting both the “hot” newer characters (like Luke Spencer) and the longtime favorites. Of course, the Luke/Laura story was attractive to longtime viewers too, because Laura, though she was young, had been on the show for ages – she pretty much grew up on the series, IIRC – and she and her family (the Webbers) were integral to the canvas.
So the reason I stayed after being attracted by the Luke/Laura (GH) and Jack/Jennifer (the DOOL pairing that drew me into that soap) plots was that they were well-crafted to link to the rest of the canvas, which sucked me into the soap as a whole. I didn’t want to fast-forward through episodes just to find my favorite characters, because most of the storylines were connected and furthered one another.
Compare that to what later became the norm. The producers, hoping to a) save money and b) attract kids, create new characters from whole cloth or SORAS an existing child character (SORAS = Soap Opera Rapid Aging Syndrome). If it’s a new character, s/he’ll be tied loosely to the current cast (“Hey! Look! Here’s a never-before-seen cousin / illegitimate child of _____!”). The character is cast with an attractive young newcomer.
Existing veteran cast members (whose salaries are naturally higher than the newcomer) are sent on hiatus or backseated to the newbie, who usually gets his/her own circle of similarly young/new friends. The veterans are trotted out mainly to further the newcomers by asking about the newbie’s problems and becoming their advisors (aka “talk-to” characters – they’re only there for the main stars to “talk to” rather than to have their own plot). Suddenly everyone on canvas is desperate to talk about this newbie and how wonderful/frustrating/scandalous/angelic/helpful they are, depending on the plot. This is different from the “umbrella” storytelling of earlier eras, because these other characters’ storylines aren’t really connected, they’re just paying lip service to the new cast. There’s nothing really linking the storylines together.
This new (or newly SORASed) character gets shoved down the audience’s throat and spotlighted in major storylines before the audience has a chance to care about them. New viewers, meanwhile, might be attracted to the young plot, but they fast-forward through the other scenes because they’re not connected and don’t seem important. And if they don’t care about the other plots on the show, what’s to keep them hooked?
So when you say “wouldn’t that place the problems back on things like writing, directing and acting, like we’ve already said?” – well, I’ve never said otherwise. The difference in writing, which in turn is due to the flailing producers trying to make shortterm decisions – then and now is a big part of the problem.