That's very much my point -it *should* have been a straight add-to-cart experience but. as you say, a bunch of requirements got added, to the point where, really, it was a bespoke item. Risk management appears to have been poor and I can think of other projects (cough:MRA4) that have underlined it.
Thing is, the DIP being unveiled apparently doesn't make much difference right now, as no-one is making any decisions til the new PM is selected - so really, Starmer hasn't done anyone any favours by producing the DIP during his last few months.
We'll see what stands or falls once we have a new PM.
If these changes do go through, I'm genuinely worried that there's an enormous amount of risk with unproven tech that makes Type 45 look pedestrian.