species extinction? what is this and why this is a problem?

Extinction refers to the loss of species or other taxonomic unit(e.g. subspecies, genus, family, etc; each is known as a taxon) occurring when there are no surviving individuals elsewhere. The extinction of any species is an irreversible loss of part of the biological richness of the Earth.
It is a problem because it has negative impacts on biodiversity. researchers suggest that species extinction has impaired at least three critical ecosystem services: number of viable fisheries(-33%), provision of nursery habitats such as oyster reefs, seagrass beds and wetlands(-69%); and filtering and detoxification services provided by suspension feeders, submerged vegetation and wetlands (-63%). Additionally, the loss of filtering services has the potential to increase the risks of harmful algal blooms(e.g.'red tide'), oxygen depletion and declining water quality. Meanwhile, coastal flooding was also increased as a result of species extinction.
In my opinion, species extinction becomes a problem because there are no surviving animals live to reproduce and create a new generation.