Innovation and a reliable (as in mature) product are always going to be working against each other. You are right to question where the balance should be.
I think as far as some, at least, of the routes planned for 230 use are concerned we have to throw in the phrase cheap and easy to run for a microfleet. Leading to
No Alternative.
Remember for Marston Vale (230003, 230004 & 230005) the alternative became a bus service. I hesitate to say (due to confidence in my memory) but was it for the best part of a year no trains ran. So in reality there was no reliable alternative to the Marston Vale 230s.
Same goes for the TfW Borderlands route (230006-230010),.
The two sent to America (230003 & 230011) are/were running where no passenger service was.
The fact is, in these cases, there was no alternative.
GWR have got 230001 working even though they had a viable alternative (165s). BUT, as
@Woods would likely say, it is for proof of concept not really proof of a future life for D78s. Innovation.
The D78s provided a uncharacteristically healthy second hand coach and running gear for trials and testing of innovation. They were withdrawn prematurely in LUs (London Undergrounds) quest for a standard sub-surface fleet.
Of course Vivarals demise has really made this innovation very difficult. It is lucky GWR (with DfT agreement/support I believe) took up the challenge. The result is a viable fast charge train and charging station that could be used for trains converted from D78 or most likely other main line stock.
One other lesson is converting trains to a different traction type is not proving easy. Just look at the 769s converted from 319s by/for a far bigger player in the rail industry (Porterbrook iirc ?). Northern are really struggling. Worse still TfW and GWR never even started trying them once built !.
Innovation never was easy - ask Stephenson et al.
Furthermore comparing to the past we only ever use rose tinted glasses and forget all the dead ends and failures.
If we avoided innovation we would still have static steam engines relying on low pressure steam to drag wagons and coaches along by cable. We should have nothing to do with this electrickery !.
230s will in the future be viewed as more successful than 769s BUT then only as a stepping stone to better things. Those better things are not yet in the present !.