There's a gap somewhere between "main road" and full pedestrianisation.
King's Road in Chelsea is an example that immediately comes to mind.
Really what it comes down to is that nice areas with approximately the right density of people have nice high streets.
You could pedestrianise Oxford Street but it'd still be a grim place to be because there are hordes of people - at a certain point the people have a similar effect to cars in that it's not really pleasant to pause outside any more.
King's Road in Chelsea is an example that immediately comes to mind.
Really what it comes down to is that nice areas with approximately the right density of people have nice high streets.
You could pedestrianise Oxford Street but it'd still be a grim place to be because there are hordes of people - at a certain point the people have a similar effect to cars in that it's not really pleasant to pause outside any more.