Society is fragmenting, the Public Sector aside the big unionised workplaces which provided Labour's core support for generations have gone and those in the gig economy don't seem to see the potential benefit in voting for Labour. As you've have pointed out it's becoming the of the well educated, socially liberal middle class - that's looking unlikely to be enough to win elections in the near future.
I can't see Starmer repeating the Blair trick of winning from the right on a "more competet/no sleaze" ticket (baffles me) - New Labour also had two policies which chimed with people back in 97 - Educatiom x3 and Tough on Crime Tough on the Causes of Crime - Starmer has nothing yet.
To recover Labour has to forge alliances of workers/supporters who will vote for it - that means supporting public services and appealing to younger voters who are finding it hard to get on the housing ladder and tapping into green politics which NIMBYs aside is left of centre, some form of Green/Red alliance - they're not gonna win by playing it safe.
I say this as someone who hopes to view a Labour recovery down South from a newly independent Scotland.