The initial lockdowns were intended to prevent a rapid spike in cases that would overwhelm the medical system. That was important, and largely successful. If such measure could have been taken in a globally coordinated, and fairly extreme manner, which was never realistic, then in theory the virus could've been eradicated early on. But that doesn't mean they were worthless otherwise.

After that period there were measures of varying strictness applied in different areas, some of which were beneficial, and some did more harm than good. Some were based on a mistaken notion that the virus could be locally eradicated. Others were based on good science to blunt spikes of infections, again to reduce strain on the medical system, or to buy time for vaccinations.

We can't look at complex issues as black and white.