You put it better than me (my sarcasm doesn't 'come over' very well). The great is the enemy of the good. Something is better than nothing. At times of shortages of funding (and political 'support' (as per HS2?) it is good to get going on what can be done when it can be.
We've rather strayed from the thread topic however the route via Marple is normally an important diversionary option for fast services between Sheffield and Manchester. Today it's the other way round, stoppers are diverting via Hazel Grove.
On 17th April LSL's White Rose is having to divert via Stalybridge and Huddersfield. This at a time when the Hope Valley route is needed for diversions away from TRU, like the Drax biomass trains.
The Hope Valley scheme grew out of planned redoubling at Dore which seems to have begun by 1999 with Railtrack planning to deliver in CP5 2003-4. It grew and got swept up into the Manchester Hub, that became the Northern Hub that delivered the Ordsall Chord, but not Platforms 15/16 at Piccadilly.
The difficulty at New Mills, and all along most of our Victorian railways, is that old drainage combined with over a century of wet and dry weather periods makes movement increasingly likely.
I understand work on the Hope Valley scheme included replacing old clay pipe drainage that in some places was totally blocked with decades of silt.