At an R0 of 2, with no interventions, eventually half the population has had the virus and (hopefully) gained immunity. Now each person only spreads it to 1 oth

At an R0 of 2, with no interventions, eventually half the population has had the virus and (hopefully) gained immunity. Now each person only spreads it to 1 other person, because the other person they would have infected is immune. (If R0 was 1, the epidemic would end as soon as the next person in the chain is immune.) This is where the people saying that the virus will definitely eventually infect 70% of everyone are coming from. Re is effective spread rate, taking into account natural immunity, vaccination, contact tracing, etc. By definition, if Re>1 the epidemic is growing exponentially and if less it is shrinking.