>look & sound fine played thru a decent video card onto a modern 60in screen.
Yeah because somebody deinterlaced it when they ripped the dvd for you. The DVD's not going to look as good as that on a pixel-array screen unless it goes through deinterlacing, either in the player or during the encoding process.

In the case of anime, deinterlacing is (usually) pretty straightforward because the original source was progressive and all deinterlacing needs to do is to grab the two fields that came from each fram and reconstruct that frame (and then set the display to the correct, possibly-weird, framerate), but there are some sources that are just impossible to do this with, such as broadcast TV rips that have been interlaced one way and then the station has put banners over the top of the interlaced intermediate and the banners are interlaced a different way. Some DVDs do the same kind of thing with hardsubbed signs and so on. These kind of sources are quite rare, but they exist because in the CRT era there were only CRTs and even if someone had a high-end monitor it was still a CRT and could just be set to 480i like a TV, so why bother accommodating hypothetical flat panels that can't do variable resolution or interlaced video?

Anyways, your files look good because someone deinterlaced the DVD when they encoded them for you, a DVD image won't look good unless you deinterlace the image yourself when you play it.