> carbon neutral
No. Poorly separated wastes in landfill cause non-trivial methane emissions and other VOCs [0]. While leachate _may_ be captured, most of the time methane is definitely not.
[0] - https://www.epa.gov/lmop/basic-information-about-landfill-ga...
For historic, sealed landfills, perhaps. Modern regulations require methane (LFG) capture for all non-trivially-sized landfills. In 2015, 74% of US household waste ended up in a landfill with a system to capture methane and convert it to energy[1], I suspect the number has increased over the last decade.
[1] https://ensoplastics.com/theblog/?p=2557