I too find the lack of epidemiologists on SAGE troubling. Cynically, I expect this itself to be a government conflict of interest; they don’t want to hear the message that epidemiologists will deliver.
Epidemiological advice is obvious, which is why it has been consistent for generations: inhibit cross-infection, by localising and compartmentalising, restricting travel, reducing proximity between people especially indoors, and providing and enforcing quarantine.
The government is caught in an ideological bind. People need money to live, but the government’s ideology is that money may only be obtained from employment, and that all production and services are best provided by massive, heavily centralised organisations. This ideology is precisely opposed to to the needs imposed by the pandemic.
We cannot choose the attributes of the virus, but we can choose our ideology.