As you're well aware, we have a first-past-the-post system and what matters in this system is the number of MPs.

A system where the government is chosen by 33% of voters has no legitimate claim to be democracy, that is, rule by the people.

This is not an actionable claim. What are you supposed to do in a multi-party system if nobody wins a majority and voter turnout is 60%? Just have anarchy until someone wins an outright majority?

In most of them you form coalitions.

That's a substantially larger vote share than any other party:

https://electionresults.parliament.uk/general-elections/6

The electoral college would throw up equally weird results if the US didn't have a fully two-party system. (How's that working out?)