Degrowth doesn't work. We take a huge hit in our standard of living if we decrease the number of people on the planet.
We are blowing through the financial inheritance left to us and sooner or later that well will run dry (to wantonly mix metaphors).
To put it callously, old people can't work much and consume lots of resources, so a plague that kills them off (however sad) actually makes life easier for everyone else.
But lower fertility rates have the opposite effect, the ratio of old people to young people increases, which is why it makes things harder.