I count 306 seats where Labour are 1st and the Conservatives 2nd, or Conservatives 1st and Labour 2nd.
In the other 326 seats, either the Lib Dems, Reform, Greens, SNP, Plaid Cymru or independents are a top two party. Where most voters live, the traditional Labour vs Conservative debate is no longer the relevant one.
With votes that close there’s plenty of luck involved in other ways. The weather, tv schedule etcetera.
It’s definitely a problem, but it’s not preclusive.
The alternative is equally terrifying - just a third of voters being the majority in the brexit referendum is unconsciable.