A peaceful childhood.

Clean water, air, and food. There’s plastic in everything. I don’t think any of us will ever get to experience any of this ever again.

Hunter-gathering

getting lost

One of your parents handling the phone to you because someone called you..

Lead poisoning. I know, I know, there are a ton of other hazards we're exposing ourselves to. We will have our reckoning with things like plastic, but at least lead is something we're aware of and dealing with.

Along those same lines, ozone layer destroying products.

Dial up internet.

Pagers.

Not being in contact with people 24/7.

Polar Ice Caps.

A time when AI wasn’t involved with everything.

Remember that time when humans had to do everything, and if there weren’t enough people around to do it, then nobody do it.

Sharing polyphonic ringtones over infrared. Hell yeah, that was pretty awful.

My previous answer to this question was about buying a phone instead of renting from the phone company. I realized that something today's children may never experience is the government actually enforcing antitrust law, and in the bigger picture, the feeling of trust that the government is there to look out for us and will do the right thing.

(Yeah, that trust was sometimes misplaced, but it existed. We also used to believe that the violators of that trust would be held accountable.)

Clean freshwater.

That feeling of logging on to limewire or thepiratebay or some random sketchy hacker BBS or irc chat.

alt.binaries.everything

Tying up the landline phone with their dialup modem.

Polio... well they might actually, depending on how anti-science their parents are and if they live in one last two pockets of it, Pakistan and Afgjanistan.