Social distancing SLOWED the infection rate down, conserving hosts, so then prevented herd immunity.
It gave the epidemic far MORE time, which allowed it to travel wider and deeper, to those who otherwise would never have likely been exposed.
Without social distancing, you could achieve herd immunity in the first month, with fewer than 60% of the population being immune through recover.
After social distancing for 2 years, you have spread it so wide that you likely would need 100% of the population to be immune before it would end.
Never do "social distancing" in order to "flatten the curve".
You either do full quarantine to totally end it quickly, or you deliberately accelerate to herd immunity, to totally end it quickly.