As far back as the 2000's, kids knew to keep their IP addresses secret. There are plenty of real-time game server architectures where no game client knows the IP address of another game client. This might not be feasible for very fast paced FPS games, for example, but that's only one particular use case.

I suspect we could significantly raise the bar to DDOS something like 80% of all websites/apps/servers -- at least to the level where random kids or even random middle class adults would think about it because they had a bad day.