I would like to have a much better feedback system on medical interventions and supplements.
For example there is as company which sells thiocyanate for hair growth in germany.
If you order their stuff from their website, you will automatically recieve an email requesting you participate in a survey about how the product worked for you: Did one experience hair regrowth, improvement or worsening of skin irritations, etc... Of course this is no double-blind study, but it still gives a good amount of data.
Same with holiday booking websites like booking.com. You dont just give a rewiew there, but points on a scale to certain questions which are important to others.
I wished that it could be somehow organized to collect subjective data from all users of supplements. That could be an incredible source of information about what could work, and what not.
I would also like to have a website for cooking, but one which directly connects the ingredients to the medical benefits, e.g. telling you how much protein and fat you will eat, but also that you will get 20 mg of Fisetin or quercetin from that dish containing a certain amount of apples and onions.