Is endosymbiosis bad?

Context: Endosymbiosis is any symbiotic relationship in which one symbiont lives within the tissues of the other, either within the cells or extracellularly. Examples include diverse microbiomes: rhizobia, nitrogen-fixing bacteria that live in root nodules on legume roots; actinomycetes, nitrogen-fixing bacteria such as Frankia, which live in alder root nodules; single-celled algae inside reef-building corals; and bacterial endosymbionts that provide essential nutrients to about 10%–15% of insects.

In endosymbiosis, the host cell lacks some of the nutrients which the endosymbiont provides. As a result, the host favors endosymbiont's growth processes within itself by producing some specialized cells. These cells affect the genetic composition of the host in order to regulate the increasing population of the endosymbionts and ensure that these genetic changes are passed onto the offspring via vertical transmission.

Answer: No, endosymbiosis is a symbiotic relationship where the internal symbiont or the endosymbiont provides essential nutrients to the host. For example, a bacteria can provide necessary nutrients to an insect.