This applies especially for the case where what goes wrong is exactly that the visitor doesn't trust ISRG and ceases to trust DST Root CA X3 when its self-signed root expires. A lot of other problems will bite those who get new certificates first, but this problem will bite every site with a Let's Encrypt certificate at essentially the same moment regardless.

So at least the blame will be spread around thinly and for most users there will be an overwhelming impression they need to actually do something on their side and not just moan and hope the problem goes away.