This is a big problem in botany. Plants and fungi have a large variety of chemical and biological interactions that is rarely able to be summed up as "parasitic", "mutualistic", "commensal", "symbiotic", or otherwise. Lots of "parasitic plants" have immense benefits to their "hosts". Some examples:

- dodder plants can act as above-ground mycorrhizal networks in the sense that they allow plants (even of different species) to alert each other of pests and other dangers

- many parasitic plants produce fruit in the offseason of their host that keeps the hosts primary pollinators alive during that season; ultimately benefitting the host by keep its pollinator alive

- ghost pipes can produce phytohormones that help its hosts grow faster and improve their immune system

But generally in botany, when we label something as "parasitic" we are exclusively looking at its ability to photosynthesize. IMO it's an archaic and very misleading term since so many "parasitic plants" are crucial ecological partners but that's just the working definition