"It's possible that there is a constant decrease in standards, such that every generation is worse than the one before it. But I doubt it."

On the contrary, that has been my interpretation of these signals since I first started hearing them.

All living things (cats, societies, lizards, civilizations) are born, have an adolescence of growth and development, then decay and die.

So there must be some brief period in the adolescence of a civilization where "kids these days" cannot be applied. Society is growing, developing and integrating.

After that brief period it may then, indeed, be possible for each successive generation to correctly identify and decry the decay of their (society/civilization).