Lockdowns only delay, so in that sense they do work but aren't a long-term strategy.
I'm not anti-lockdown where it has a benefit (like waiting for a vaccine). Locking down until a vaccine came along was incredibly risky, but has worked out for Aus/NZ, or at least it was working pre-Delta. Whether lockdown will stop Delta spread is less clear. I think that Australia will be in either constant lockdown, or continual cycles of it, until they decide to let it spread.
However, not many people have come to the realisation that Delta changes everything because Herd Immunity by vaccination alone is no longer possible, and that a large wave of infections is now inevitable everywhere. Europe is just starting to see this wave and it will be quite bad in places with low immunity. The UK will fare much better.