The assorted things that have burned or exploded when I left them in my microwave oven too long suggest that this is not entirely correct.
Ionizing things is not the only mechanism by which radiation can cause harm. It's the only one known to be able to cause cancer, which seems to be the main thing people worry about, so it would be accurate to say non-ionizing radiation cannot cause cancer.
The non-ionizing ways radiation causes harm also tend to require high intensity and prolonged exposure, so it is probably accurate to say you don't have to worry about them unless you make a habit of, say, hanging out directly in front of high power microwave antennas.
You also realize that a microwave is designed to use a frequency band that sympathetically excites hydrogen atoms, while 5G is a collection of technologies that use UHF, high microwave, and submillimeter bands that do not sympathetically excite hydrogen, right?
Climbing to the top of a 5G antena while it is working and hugging will probably get you a few burns.
I also worked for some months with infrared and green laser that were powerful enough to cause eye damage. And if you want a less technological example, with a glass lens you can concentrate sunlight and burn many things.
Perhaps a better statement would be, "Non ionizing radiation is safe when RF exposure guidelines are followed."
The main problem with multimedia is that they don't have some specialist to cover the news and they just copy&paste the press release of any study floating around. So they make a big scandal about in a study that report like 20 subexperiments and only one of them is statistically significant with p < 0.05.