Is this a production problem (we physically won't be able to produce enough stuff and provide enough services) or an economic problem (we won't pay people enough to support everyone).

Or is civilization just a giant ponzi scheme?

Every sperm is great.

If a sperm is wasted,

God gets quite irate.

I doubt that anyone could imagine that someday, that might not be satire.

The biggest factor is that people want smaller families or no family at all. The sperm part doesn't matter if the desire/will isn't there.

Plus, this is only an average, so there will likely be plenty of potent people left to continue the species with their, (controversial) better in this respect, genes. Not to mention medical interventions.

Less human reproduction is not a crisis.

We have dropping testosterone levels, outrageous obesity levels, anxiety, depression, autism, other gender and sexuality abnormalities, cancer, auto immune diseases, cognitive problems, etc.

We figured out that we shouldn't put lead in paint & gasoline, that we shouldn't put asbestos in our houses, shouldn't handle mercury with our hands. But there are thousands of petrochemicals coming into contact with our bodies every day now, and surely some of them are endocrine disruptors, carcinogens, cause reproductive health issues, etc. Yes it's a crisis.