Has not been my experience with two children under 10. YMMV. I would pay much more than I pay today for the walkable and bicycling I’m able to have when in BCN (vs say, Chicago).
In Barcelona? I do, and have never had a problem like I had in the US where I was afraid someone wasn't paying attention and was going to hit them (with multiple near misses). Call it urban planning, call it people in a European city taking more care, whatever the root cause, that is my anecdotal observation. You can always compare vehicular pedestrian deaths in the US to those in Europe if you're looking for something more data driven.
We are not discussing general accident figures on normal streets.
We are discussing the comment you replied to: "the planners' great idea of mixing cars and people on the same street." which was in reply to a link discussing that idea.
And you wrote that you thought that was safe for 10-year-olds.
Which it is not. A street with pedestrians and cars on it is called a "street" and is not a safe place for any pedestrian, let alone a 10-year-old. Which makes it a stupid, dangerous idea, but one that is cheap for the planners to implement, hence its popularity.