As for technical attacks, I'm not an expert but I'd assume it's more difficult for bad actors to bring down decentralized networks. Has the BitTorrent network ever gone offline because it was hacked for example? That seems like it would be extremely hard to do, not even the movie industry managed to take them down.
With the 30-second "time to first byte" speed we all know and love from IA, I'm pretty sure it'd only get faster when you're the only person accessing an obscure document on a random person's shoebox in Korea as compared to trying to fetch it from a centralised server that has a few thousand other clients to attend to simultaneously
Depending on scale that’s not necessarily true. I find even today there are many services that cannot keep up with my residential fiber connection (3Gbps symmetrical), whereas torrents frequently can. IA in particular is notoriously slow when downloading from their servers, and even taking into account DHT time torrents can be much faster.
Now if all of their PBs of data were cached in a CDN, yeah that’s probably faster than any decentralized solution. But that will take a heck of a lot more money to maintain than I think is possible for IA.
Risk management is a balance, not fearmongering as you say. That's why I'd rather use advice from people with daily experience than look at the newsworthy experiences ("nothing happened today, again; regular security patches working fine" you'll never see) and conclude you'd attract threats and cyber attacks just by hosting backup copies of parts of the Internet Archive