There's plenty of reasons why the 2016 referendum and its consequences was undemocratic — I thought at least that was accepted by Leave voters by now? Here are a few anyway...
- Misinformation and lies throughout the campaign, following on from years of anti-migration and anti-EU narratives in the press made up on falsehoods.
- The 2016 referendum was badly designed — Leave weren't required to offer an alternative, hence the multitude of versions of Brexit debated after the result (Single Market, EEA, Norway, Canada+ etc).
- EU citizens who were UK residents couldn't vote (many who have lived here longer and contributed more to society than I have, and I did get a vote).
- Vote Leave broke election laws, and there were no repercussions for overspending.
- UK press and media, including the BBC, is not regulated enough to be forced to require facts to be balanced with facts and empirical evidence; emotion and ideology will do in this post-truth era.
I thought your comparison to a rugby match was interesting. Sport is flawed with bad decisions and injustices (that's often what makes it so compelling), and has a varied history of corruption.
To think democracy won is deeply misjudged, and simply naïve at best.
Hope this helps answer your question.