Ultimately the entire "Full Y" network needs completing to fully realise the benefits and for the business case to make sense. Ditching the eastern leg was the first, and worst act of vandalism on the project. Without it, the East Midlands and South Yorkshire see no real uplift in capacity and reliability. Dropping Golborne was the second act, taking Scotland off the high speed map, meaning the retention of domestic flight to Heathrow for the foreseeable. Delaying 2b was just strange, because delay won't save any money at all, and it wasn't done to make modifications either. It was ready-to-go.
Where we are now with 2a, 2b, and even Euston potentially being dropped makes the whole project ineffective at doing anything it was designed to achieve. There's likely a lot of political strategy at play making it seem all things are on the table, when in fact many who don't even support the project want its to get to Euston at this point.
To me the most logical way forward is to at least commit to Euston and 2a, even if it means 2b gas to take the hit for the time being. Of course being from the Manchester/North Cheshire area personally I'm quite invested in seeing it done. The delays/limitations through Stockport are a huge hinderance to the overall network. 2b Solves this.
I don't truly believe NPR would ever utilise 2b infrastructure anyway unless it's part of a true East-West high speed line. It'll definitely involve using the existing transpennine route, possibly with a few cut-offs and a new route through Mar city centre at most. So by that logic (where 2b is just for HS2) it's still vital to unlocking capacity in South Manchester, but not make-or-break for other northern cities. In fact Scotland would benefit far more than Liverpool.
Commit to Euston and 2a, leaving it open for future phases. Start building it and concentrate on east-west capacity improvements, whether that's a Castlefield bypass, a new route into Liverpool from Eccles (avoiding the densely populated L&M line) and getting that through station in Bradford connected to the TRU route via a new stretch of line. Each of those projects can be delivered independently, are controlled in scope and geography, and still things politicians can "cut ribbons" for.
The mismanagement on the government's behalf of HS2 has been shocking, without that we'd be in a much better place. We are where we are though, and a level of strategic pragmatism might be necessary to get things moving, rather than being stuck in limbo.