I would say that 95% of boaters don't use it anymore as GPS has become cheaper and more accurate and overlays with graphical maps.
I'd guess the number is >>99%. I'm pretty active in the boating
community and don't know ANYONE that still uses a LORAN.
There's no reason a LORAN couldn't drive a chartplotter (except that
while LORAN was very repeatable (the same numbers would put
you on the same rock) it wasn't all that accurate (the Lat/Lon was
often off by a few hundred yards.)
And you could probably build a LORAN (in production quantities)
for about the same price as a GPS, though it would need a good
size antenna because the frequencies are a LOT lower.