I'm 30, and have both.
Instagram is choc+a-bloc full of adverts, influencers and people showing off. Most people on there are under 30/35, and there seems to be endless streams of people videoing their nights out , ( which doesn't seem very spontaneous to me). There seems to be no sense of community there , and cannot share anything that's not a picture.
Facebook on the other hand , seems much more of a community. People of all ages use it. I enjoy seeing my great aunt's holiday pics, or photos of my dad's neighbours cat. The pictures are funnier, warmer and it's much nicer to see my friends kids easter egg hunt than endless video streams of someone's night out or smashed avocado. It seems to have a much wider reach.
I've seen people genuinely helped by community Facebook groups, and special interest FB groups. People can still enjoy/ share / debate political content.
AIBU to say I don't get why Instagram is more popular, as Facebook just seems better?