Well, unless you're claiming Marcus Rashford's tweets are now the MSM? ;-)
I appreciate your points about web traffic, but I think you're maybe taking a rather simplistic view on it. Even though 300,000 hits a day may seem like small-fry in a population of 65m, I don't think it's that straightforward.
Loads of people keep up with the news based on what other people share with them, whether in person or online. They go to friends, family, even celebrities who they consider well informed of news and current affairs.
But those "well-informed" people are getting their news from somewhere - the BBC, Daily Mail, Guardian, wherever. Even if national newspaper's circulation and web hits are dwindling - they still play a huge role in setting the topical agenda and being a source where other influencers get their information.
As social media increasingly drags people to the extremes of left or right of opinion, it seems inevitable that the two most polarising newspapers - the Daily Mail and The Guardian are increasing their market share, and influence.
It's almost become the go-to insult if someone's opinion if more left than yours to say "Stop reading The Guardian" or if their opinion is more right wing than yours to say "Stop reading the Daily Mail".
Although these two news outlets may be struggling commercially, their influence on setting the discourse is pretty robust.