I think the left’s problem isn’t inclusiveness (in things like this) it’s the inability to give power to “strong” leadership. The same mental firewalls that prevent those on the left from falling victim to mountebanks keeps them from letting others speak on their behalf.
It also creates mental roadblocks for anyone on the left who tries to lead. “How can I speak for these people? I am not one of them.” That’s not a limitation of inclusiveness it’s just empathy. So when anyone on the left challenges a left wing leader with anything, really that leader–if they are truly left leaning–will not fight back without near certainty about their position.
This makes it easy for a left wing leader to denounce the illogical and/or racist positions from those on the right but extremely difficult to take a stand on issues where everything sucks like Israeli/Palestinian conflict or immigration. This leaves them open for charlatans to point to them and say, “See? They’re weak!” Which is the exact thing the right hates and fears from left wing leaders.