What it does not promise

Compounding is not a plan and not a guarantee. Real returns are uneven, some years are negative, inflation eats part of the gain, and every projection you have ever seen used a smooth average that no actual decade produced. Anybody selling certainty using this idea is selling something.

What it does honestly support is a modest habit: put something aside regularly, leave it alone, and do not check it often. That is unexciting, which is precisely why it is undersold — and it is the part of personal finance that most reliably works.