It's exceptionally popular in British culture to go around calling things 'White Elephants' or describing them as a waste of money for no reason at all beyond that you personally find some small element of them objectionable.
Indeed, it's why if we are going to look at cancelling any part of HS2 the metric for doing so should be "are we likely to be close to the predicted passenger numbers or not" only is we are likely to fall (say) 15% below the predictions should we consider cancelling it.
Pre Covid it was clear that we were unlikely to meet this metric (as we were above the expected passenger numbers for a few years in the future, let alone where we were), however Covid has muddied the water as we still aren't sure what the ongoing passenger numbers are doing to be.
Although things would have to be fairly dire for the likely passenger numbers to be 15% below the predicted increase in passenger numbers. Including a continuing fall of 35% and then 3.1% or lower growth assuming a future year of 2038.
However even then rail growth would have reached 185 passengers for every 100 passengers in 2009 and so chances are there'd be a need for significant improvements along the lines of HS2 within a decade of them anyway.
As such, the likelihood is that we might as well get it done, have the benefits (including the ability to have policies which discourage most internal flights, and so significantly aid our ability to reach net zero by 2050) and not have to restart it (or something like it) in a few years when passenger numbers continue to grow.