In the US I am pretty sure we are already on the decline.
I think it has to do with, during the industrial revolution and post-war, huge scientific advancements and tech grew the economy, fed capitalism by means of providing new desirable goods to consumers (e.g. dishwashers, nicer cars, etc.)
I wonder if we've reached a "peak" of consumer comfort where advances in science/ tech/ medicine are no longer frequent/ impactful enough to meaningfully satisfy consumers, (why do we care about exploring Mars?) so it's easy for people to reject it and say "we don't need science."