I honestly don't get slides for high school? Is it effective to teach? Or just easier to teach? In my education we copied the black board by hand, and that al

I honestly don't get slides for high school? Is it effective to teach? Or just easier to teach? In my education we copied the black board by hand, and that allowed us to learn how to summarize information. Writing by hand also improved memory. And seeing the teacher thinking and choosing how to present the information in real time had a lot of value. Further I find it way more difficult to make a slide presentation that effectively teach something than only having a blackboard that forces us to really explain the steps. At uni I teach with slides, but they are done in a way that mimics blackboard writing. It takes an enormous amount of time to make them, but the students are very happy. What are your opinions?