Reforestation does not replace conservation. Most trees are planted for commercial purposes, which usually means monoculture. These kinds of forest don't support the same species whose habitats have been destroyed. Tropical rainforests in particular are most likely irreplaceable.
Having said that, commercial tree planting is still very important to keep demand for wood away from natural forests.
Also, cutting and possibly burning, even if trees are later planted, usually destroys soil and consequently water cycles. Poor soil with bad water retention means water, even soil runoffs, floods, and consequently water shortages.
Commercial wood forests tend to have shallow soil and poor retention.
Having said that, commercial tree planting is still very important to keep demand for wood away from natural forests.