For the reason that it would be the Coalition being talked about if Labor had been in government for years and made a mess.
In any situation where someone proposes a change, the onus is on them to convince those making the decision that the proposed change warrants the risk of uncertainty versus the devil they know.
That goes for anything from who runs the country through to your household appliances. If there's something already in place and I'm proposing to get rid of that and replace it, well the onus is on me to convince whoever's making the decision that this would be a good idea. In the absence of that, by default the existing arrangement is the lower risk option since its downsides are known.
It also comes back to the point you make:
And yet despite all that and much more, Labor still hasn't managed to win in recent years.
That's a bit like saying that if I'm a runner, and I turn up at the track and find that there's a few real professional athletes there including one who really did go to the Olympics well then I've got a pretty good excuse for not winning that race. Nobody's going to say I'm crap if the competition was clearly brilliant and I still finished in a respectable time. Even the harshest critic is likely to point to the professionals and that they were bound to win.
If however I turn up at the same track and there's an assortment of unfit, overweight people wearing gumboots well then I'll be judged far more harshly if I don't win that race. Given how hopeless the competition is, it's an equally harsh reflection on me if I can't beat them.
Personally I'm not rusted on to either party but I can see why Labor hasn't been winning elections at the federal level. In short, the party hasn't convinced the masses that it has real, actual solutions to the problems so many are facing indeed it seems uncomfortably close to those who want more of the same.
That latter bit's what does the real damage in my view. Being perceived as too close to the wrong people.
The Coalition is shocking in my view but if Labor wants to change that, if they want to get elected, well the onus is on them to convince the masses that they actually do have a better plan. That they've failed to so is a failing in itself and that weakness ultimately enables the Coalition to get away with so much.
Or in other words - a weak opposition begets poor government and vice versa, a strong opposition forces the government to lift their game too.