Herd immunity without vaccination takes time (usually years), is usually only effective against pathogens that do not rapidly mutate, usually only possible in relatively isolated populations without carrier exchange with other infected populations, requires a very large portion of the population to develop sufficient antibodies, and virtually ensures maximum potential severe outcomes and deaths over the course of development if there are no additional measures for population isolation and infection mitigation.
So using it as a sole real method of containment (even paired with optimised personal hygiene and social distancing) is the near equivalent of just letting the viral outbreak run its course and hoping for the best (i.e. that collectively the population will generate antibodies to the novel coronavirus sufficient to allow for the slowing of transmission until comprehensive vaccinations can begin).
Just want to clarify for those trying to determine if the strategy of attempting to build herd immunity in 6-9 months is the optimum path.