I propose a new approach: Rather than given treatment vs not given treatment, we instead vary the dose slightly, and we include the whole world in the trial.

Ie. instead of taking 100mg of Advil, instead you will receive somewhere between 95mg and 105mg of Advil. You won't be told how much you got - but the barcode on the box will encode that info. That already might be the case due to allowed inaccuracies, but now we're gonna measure and record it.

Later, the data of which box was dispensed is combined with any other relevant medical records, and across the hundreds of millions of people involved, any benefit/disadvantage of a small increase or decrease in dose will become apparent.