For some that's definitely true. It's well known that light (especially Edit: blue-to-yellow as per below) can disrupt someone's circadian rhythm.

Night owls have been a thing since long before cell phones existed

That may be true, but at least the genes for night owls are present in more people than the genes for early birds.

So it should be expected that, regardless of phone usage, over half of the population will go to bed and wake up ~2-3h later than expected.

If your timezone is closely aligned with the sun, that'd be 22:00-06:00 for early birds and 01:00-09:00 for night owls. But if your timezone isn't, both of these times would shift around.

For me personally, no matter when I go to bed, whether it's 22:00 or 03:00, I always wake up precisely 09:30 without any alarm clock. But this also means if I have to wake up earlier, e.g. at 8am, I'll be very tired and not well rested.

I am typing this in Wuhan, listening to birds singing in the middle of the night. Are they owls? No, their sleep patterns have simply adapted to the constant neon lighting all over the place.

Depression and alcohol can also negatively affect sleep patterns.
Combine depression with all night TV binge watching or phone soon browsing for a greaaaat combo.

One can break cycles, though.

And definitely a lot of it is just that people have gotten used to it. People think they have insomnia because every time they try to go to bed early they can't sleep but they're doing it the wrong way. They should wake up early and go to bed when they start to feel sleepy and work on sleep hygiene (including even a short walk outside). It won't be fixed in a day.

It also changed with age for me. And I feel like I also influenced it by getting to bed on time almost everyday, and putting away the phone.

So I understand that it might be very difficult, it was the same for me, and I managed to change it.

Still feel tired if I have to wake up before 7 am, no matter how much I slept, but that’s mostly avoidable.