The implicit claim here is that one can claim that the internet, in some legitimate continuous sense, is 60 years old, and that it started being useful to the general public circa Y2K.

Going by that standard, decentralized blockchains have been around for about a decade... and should get two more to develop "an extensive track record" of practical applications.

I don't actually think this is a useful comparison — but it is hardly one that does a disservice to blockchain.