Long gone because the option has gone. I suspect (but don't know) those are peak viewing times for the kids channels, but unlike back in our day the chances of having new original UK content at those times is slim.
Children's programmes achieved the viewing figures that they did during the heyday of analogue TV because of scarcity. The idea of children's programmes being available 24 hours a day was just a dream to most kids, so whenever the rare chance emerged to watch such programmes - like weekday afternoons and saturday mornings - millions of kids up and down the nation would huddle around the TV because that was the only opportunity that they had.
I will even admit to watching CBBC on a TV in an electrical shop whilst out and about.
The creation of CBBC and CITV channels followed by the analogue switch off technically rendered children's programmes on BBC1 and ITV1 as redundant.
I'm not so sure about peak viewing times but availability of children's programmes throughout the day now means that viewing times are more varied.
I'd imagine most kids still like to crash out when they get in from school and watch a bit of TV just as their parents do with The Chase and Pointless when they get in from work. One key difference though might be that for many kids the school day now extends into after-school clubs etc. pretty much daily with schools pretty much expected to provide for children whilst their parents do the 9-5.
I preferred the internet when it had a sense of humour.