Quick answer
Work produces something. Talking about work does not, and the verse draws the line exactly there.
Read both lines
The NKJV footnotes the second line as literally talk of the lips, which is more specific than idleness: this is not a lazy man but a talking one, and the distinction is what makes the verse bite. Plenty of people are busy discussing what they intend to do. The first line is generous by comparison, saying that all labor has profit in it, including the unglamorous and the unnoticed. Set against verse 4's dirty stable, the chapter is twice recommending the same unappealing thing: actual work, with the mess and without the commentary.
Related: Proverbs 14:4 · Proverbs 12:11 · Proverbs 28:19
New King James Version®, Copyright © 1982, Thomas Nelson. All rights reserved. Full copyright information. Scripture provided by API.Bible.
Go Deeper
If this verse has been used to put weight on you that it was never carrying, ask about it directly.