The trouble is, there doesn't seem to be any reason to believe that test, trace and isolate can work effectively. The characteristics of Covid-19 - infection just from being in the same room as someone with no symptoms, low mortality, lots of asymptomatic cases and non-specific symptoms in most other cases - do not seem even remotely amenable to contact tracing-based approaches.

Supposedly, Singapore and South Korea were proof that this could work anyway, but it seems to have failed in both places - Singapore had to give up and lock down after cases exploded, whilst South Korea also had a whole bunch of spread that completely escaped contact tracing and nowhere near enough testing to pick it back up again, but somehow managed to reverse it through stricter social distancing measures well short of a full lockdown for reasons no-one has explained. I'd be very interested to see what serology studies have to say about South Korea's actual infection rate.