Just to add my experience... DS is autistic and stopped going to school in Y7, just before COVID. The following four years were the most traumatic and stressful of my life. The threats of prosecution, the utter despair of how to help him, the devastation of him missing out on life... It was hell.
We tried absolutely everything. We saw every professional we could think of, went on courses, read books, removed devices, shouted, hugged, chatted, spoke of his dreams for the future.
However, the fact is, he simply couldn't face the noise, the crowds, the sensory overload of school. He spent his days asleep in bed.
I'm a teacher. DH and I both value education. However, schools are simply not equipped to support certain children. No matter what we did, he wouldn't go.
My DS ended up leaving in Y10 and attended a specialist college, where he did well. The following year he left and went to mainstream college, where it all went downhill again. They refused to let him resit his GCSEs. We have spent a lot of money on tutors and exams. People think you have to do GCSE resits until 18. You don't. The LA doesn't care.
DS is now looking for a job, with the help of a support worker. How he will achieve this with very few qualifications, I don't know. He is such a bright young man, with an amazing general knowledge and a lot of ambition, although lacks confidence.
Anyway, to answer the OP, as others have said, these young people have always been around, you just didn't hear of it. I never thought I would have a child who refused to go to school, but I did. To anyone who thinks that it's a certain type of family who has a school refuser, it's really not.