There was a whole herd of quality engines, names that are now lost in the mists to 99.999% of the population, but there is no getting around the fact that Listers couldn't sell their own CS engines, and you RN twin is an example of why.
I worked quite some time in the private yacht market, nobody wants engines like these any more, even on true displacement craft where ballast is good, they want compact, therefore high revving, light, therefore cheap to fit, generic motors, because the smaller the motor physically the more you can hide it in some tiny cubby hole somewhere and the more you can lay out the interior to maximise the impression the boat is twice as big as it is.
L Gardner & Sons is a REALLY nice example of "rolls royce" lister, they took everything lister did to make sales impossoble and went further, gardner made their own injection pumps too (how many diesel "makes" can you name that do that?) fabulous quality, horrendous expense, every engine still hand assembled and this is tracked so you can go back to the factory and meet the men who built your engine, or the sons of, or grandsons of.... and the actual quality and ingenuity surpassed lister in many areas
For every CS lister didn't / couldn't sell, Gardner shouldn't have sold ten, yet Listers dropped the CS line, and Gardners can still sell all they can make.
Part of this is quality, in traction applications a million miles on a crankshaft (eg original bearings) was not exceptional enough to impress anyone at the factory (I know a marine gardner that motored accross the north sea with a broken crankshaft) in fact you're likely to get comments like "we don't require customers to inform us when our motors are run in, but thanks for letting us know"
Part of this is non-stationary, which would have been an easy mod listers never bothered with
Mainly it was piss poor management, just like truimph mptorcycles telling its engineers the nips could not build anything to compete, weeks before honda launched the sohc 750-4, and then management claimed they wouldn't sell because customers always bought british, not oriental rubbish.
Lister is still going, but they're not that big, and only ministry of defence contracts and such like kept them going while they learned hard lessons in economics and marlket forces.
The lister CS is a (to me at least) 1950's incarnation, and it only makes sense to people like us because we are living some part of our lives in 1950s style, instead of the rampant credit card fuelled consumerism buy use dispose buy again way we are supposed to today.
the RN is another anachronism, they'll sell maybe 20 a year, and that keeps them happy, but there's no future in it.