There's no better treatments coming. We've been fighting viral pneumonia since the dawn of medicine and the tool kit is pretty sparse. Finding anything nearing a cure or even a 20% improvement is wishful thinking.
Our health care capacity is adequate. NYC got to ~30% infected and while I'm sure none of the medical workers want to repeat the experience the level of care remained good. Any capacity increase is going to come with only marginally improved outcomes.
There's no purpose in extending the lockdown. Either we can get back to something resembling normal life and control the spread or we can't and everyone gets infected. Extending the lockdown is just delaying that day of reckoning.
The comment you are replying to should have also mentioned greatly increased testing capacity as well as contact-tracing. Extending the lockdown allows us to build up this infrastructure so that restrictions can be reduced while still preventing exponential spread.
Basically, all of the US media reporting around testing has been terrible, misleading, partisan nonsense designed to create an imaginary testing gap that can be blamed on the current president to try and kick him out of office in November. Publications like the Times are quite open about why they're doing it. The UK isn't much better though.