I can only speak for me and my DD. DD is 9, in Y4, and I left primary school in 1980.
I would say that DD is having a much happier, more engaging and kinder time at school that I had. She often comes home and tells me about stuff like 'X cried because Y and then we all talked about how we could help and we came up with ideas for X to try'. There is an emphasis on emotional security and supporting others at her school which I find just wonderful. Quite honestly, any 9 year old who cried at my school would have had the piss ripped out of them mercilessly by their classmates. It was accepted that children hit each other sometimes, that some people were just stupid, that it was OK to engage in what would now be considered bullying. This was a nice middle class primary in leafy greater London (now considered Outstanding by Ofsted though am sure lots has changed - DD's primary is rated Good and is maybe a couple of miles away from my former school).
I also think the space for differentiation is really amazing. When I was DD's age, we all did exactly the same thing at the same time and some people were bored stiff and others were totally disengaged because they had no idea what was going on. DD happens to be really good at one particular thing and her teacher has really gone the extra mile to find stuff that is interesting for her to do, letting her work on projects that she has dreamed up herself and generally making absolutely sure that DD is not bored. Equally, I know from talking to friends that children who are finding things difficult are supported with lots of one to one and small group work to help them catch up. In my day, you just got sent to the remedial class but I do not think that it was particularly effective, judging by the outcomes. And DD is very aware of differences and the need to be kind to those who find things harder. In my day many children called the less able children thick and those of us who were more able were ridiculed as brainboxes and eggheads etc. You had to fit in and be the same as everyone else to be liked (it was OK to be good at sport).
With respect to the curriculum, I don't know what ours was. I arrived at junior school able to read, write and do basic arithmetic. I left in much the same condition four years later. I had studied the Tudors three times and the Romans once without learning anything about any of it. I can't remember any science, any music apart from singing, any art apart from 'paint/draw a picture of X', any geography, any MFL or anything else much at all apart from endless sodding netball/rounders and a little swimming. DD has had a go at hockey, netball, rounders, dance of various kinds, athletics of various kinds, football, tag rugby, swimming, gymnastics. She has had recorder and guitar lessons entirely free so far and will learn the ukulele next year. She has studied several different artists in about as much depth as a child of this age might be capable of (cannot remember all of them but Paul Klee, Monet and Jackson Pollock have featured). She has attended clubs at school that range from yoga to sewing to choir to French to cross country running to science to art to basic engineering (lego with electronic stuff) to coding to chess to orchestra to keyboard (as in piano) to ukulele. There are loads of them. Most are free or cost a quid or two per session. Not only are they interesting but lots are before or after school so are essentially providing v low cost childcare to allow parents to work. I think we had a chess club but nothing else apart from a school orchestra.
It is certainly true that the new curriculum is more challenging than the previous incarnation. Not sure what I think about this. In the days of O levels, only 20% of the cohort passed them. I am not sure that that is a good way to run things. We do need to provide everyone with qualifications that show what they have achieved. What is the point of tons of people coming out with fails that don't show that they have at least achieved basic competence, which most do? DD will be fine with higher expectations but I can see that many of her classmates won't (and it won't be for lack of application).
In case you think I am bragging about DD's school which, despite a few niggles, I find mostly incredibly good, this is the least popular school in the area. And it's the least popular school because it doesn't give a stuff about results expect insofar as people are achieving their potential. I know for a fact that other schools locally are not focused on quite the same things. So it's interesting. I chose a school which is considered bad by most local parents. But actually it's worked out as the very best I can imagine it could. Although more than a few days' notice of dressing up days etc would be really good, thanks.
It is definitely true that even with the more challenging curriculum and higher expectations, schools can still achieve an environment that's a happy place to be for children.