Am gonna start this from a different end.
Have you decided your strategic choices and sense checked them on the which medschool megathread?
https://www.thestudentroom.co.uk/showthread.php?t=7312527If you have and you know where, have you spent some time trawling through their websites to find out IF they use the PS in their interview selection (1) and admissions process as a whole (2).
If you have done that, do you know HOW they use it,and at what stage , and what they are looking for?
Does your PS hit those points ? Does it have a fair bit of reflection in it ?
If it has all that stuff you may find that the first bit about why, is really squeezed.
The details might be something that you can expand upon at length at the interview.
So, I agree with the poster above that it could be the system not the people. But equally the why, is it the health ineqality? Why is that important to you? Rather than what is broken. You will want to have the answer for a suggestion for your interview. But for me it's the why, not the what.
And, it's very very brief. So personally I recommend not going for something that is ultra complex to explain in a short sentence.
Disclaimer:not an admissions officer 😁