Vinegar is an Ok solution if used properly.
I have been cleaning for quite some time and have found that Vinegar is the most inexpensive way to clean and maintain. However, I find that alternating the cleaning with another cleaner is also a great solution to losing that shine.
With time, vinegar does take away the shine of furniture and an occasional spread of Pledge on your furniture will maintain it's original finish. Many of the houses we clean alternate their floor cleaning with vinegar and something else. Basically, it still remains the best solution for high traffic areas in homes and offices.
Use a damp quality towel/rag that absorbs as you clean. Using an excessive amount of water is the culprit of destroying hard wood floors, more so than vinegar.
Also, vinegar is most acidic in it's pure form. When properly diluted, it still may eat away at a weak finish, but it also kills 99% of bacteria, 82% of mold, and 80% of viruses.
Using alternating tactics and using vinegar properly is still safe way to clean.