@bthao you would be surprised on how many "old" bugs remain in modern systems still exploitable. Take the cellphone SS7 exploits, they have been around since 3G and still wont be fixed in 5G, that's over 15 years.
@Septem The original Morris Worm wouldn't work on modern systems.
Two of the three programs it exploited aren't even installed on modern systems. One can't even navigate NAT, rendering it unusable on a modern network.
The surviving part of the target, sendmail, has been oompletely rewritten since then.
only way I could see something going morris worm level these days would be if someone got the intel speculative execution bugs to work in javascript, and if they where hardcore malicious enough not to just use it to make a quiet background bitcoin miner and get stupid rich.