If you or I devoted our lives to good causes, we would only get recognition for those lives immediately impacted by our actions. Similarly, if we wrote to the PM, our letter would be filed very quickly.
It takes people with a media profile to garner support from the masses and this is exactly what Rashford has done, to his great credit.
By all means, criticise him on a footballing basis because he's not been very good, albeit that he would be very welcome at Swindon. However, I think it's churlish in the extreme to criticise his efforts off the field because they resulted in significant benefits for those with no voice.