Thinking of the Tony Benn quote about politicians being "signposts or weather cocks", I would guess that the centre of mass of the electorate has drifted ever further to the right, leaving Labour with the choice of being the signpost, waiting in the wings (for years, if need be), pending conditions changing to bring them back into favour, or they have to be thr weather cocks, perpetually shifting position, pandering to voters , trying to scavenge votes.
The trouble is, that behaviour leads to the generic policy of offering the electorate sweeteners, conjoured up using --bank loans--. The banksters love this and doubtless have the power to shape public opinion such that Labour's nose ring is pulled this way and that, frantically borrowing more to please this or that pressure group.
Socialism will always fail due to the sheer numbers of the kind of people they purport to help. You want to give nurses a pay rise of £100 (a paltry sum, each, if this is per year)? That'll be a few million which you can't otherwise spend on patients. There's only one chief exec, so their pay rise could be five figures without cramping service delivery.
(Well, these are the standard excuses, in public sector pay negotiations).