I think a lot of what's already been mentioned - and the things along the same vein that I'd add - boils down to the effort things took, the long anticipation and their limited availability, which made them seem more special. What Mrs Doyle would refer to as 'the misery' 
I'm so glad to have the internet now and would never want to go back to not having it; but at the same time, I miss many of these things that were once so significant and are now just a two second click if you can be fussed.
I remember once spending hours in a public library trying to find the answers to a tricky general knowledge prize crossword. Nowadays, you'd have the answers in a couple of minutes tops - and quite possibly could just type in the name of the magazine and 'crossword' and find that somebody had put all the answers there to see instantly. In hindsight, today is so very much better in every conceivable way.... but....
One other thing that we freely enjoyed as children and young adults was the ability to make stupid mistakes and rash decisions (obviously not talking crime-level here!) - and nobody would record them, no filming, no photos, no uploading or documenting on SM or anywhere else online. Our many moments of impetuous idiocy were simply forgotten forever, except maybe in the deep recesses of one of two close people's memories. Middle-aged people like me have known the contrasts and had been around long enough to know, by the time the internet was a general 'thing', what you could seriously live to regret doing; but younger generations will never know that.
It makes me feel about 500 years old to think that, if we'd been warned about online safety as kids or teenagers, we would have assumed it was a caution not to play near the railway tracks (or possibly about receiving dodgy landline calls from weird strangers) - and that is all it could possibly have meant.