Buddhism do not burn gold, silver paper offerings but uses fruits, incense, flowers etc. to offer to Buddha. What is its significance?

Gold and silver foil paper offerings are meant for ghosts and spirits, the Buddha has no use for it. Offerings to the Buddha is a way of expressing our sincerity and respect.
If Buddha is really to have use for it, then going by Buddha’s great compassion and his advocate for no killing and strict adherence to a diet of vegetarian food, that is why offerings of only fruits, tea and similar items are used.

There are many items to offer. Overall, non-killing of lives is the main principle. When we examine in detail, each item for offering has its own significance.

In the act of offering, fruits are food that symbolizes zen, incense represent diligence and the dedication of oneself to progress, flowers symbolize endurance, candles symbolize wisdom and finally, tea which is water, symbolizes charity and giving.

Extracted from:
Elder Li Bing Nan’s
《Buddhism Questions and Answers》Common Question No. One of One