I agree with your point DM as far as it not being part of the community, but, what is good for Sale is also good for Salford Fans travelling from other parts parts of the Manchester area and Away Fans so it doesn't quite stack up. Although yes the vast majority of Sale home fans will be travelling
BTW the grounds are about 5 miles apart and there is plenty of connectivity between Weaste and Peel Green even if you had to go via the old ground to get to the new one. I don't get that many Salford Fans will be starting their journeys in Manchester City Centre or historically relied upon a tram from Piccadilly to Weaste it certainly wasn't around for the most part of their history.
Salford's fan base IMO or lack of it is due to the make up of Salford as a city, it's spread out and not really one community, there is a great appetite for Association Football, they've had little to shout about since the early 70's and even then crowds weren't in 5 figures, I think the last game ever at the Willows attracted 10,000 but week to week the club relies upon a hard core of less than a third of that number. It's a tough sell and yes the ground could be in a better location and they've lost some fans in the moving process but the thing that would get people taking about and attending RL in Salford is success.
They could double their numbers and if they ever got to Wembley then they'd take plenty for a day out the trick being able to retain some of those fans