There’s a big distinction to draw (which I rarely see drawn, for whatever reason) between the sort of large-scale veining / creasing that happens when rigid denim is put through a harsh wash—think rinsed or dyed Tender Co.—and the sort of small-scale marbling that happens over time when tightly woven denim is put through the washer and dryer repeatedly. I think the latter sort of “marbling” is appealing to a lot of folks here, myself included, whereas the former sort of “marbling” is often seen as more unsightly.
Personally, I wash my jeans inside out with low (or no) spin for usually the first half dozen or so washes, until they’re starting to soften up and lighten up appreciably, in order to avoid any big veins. If they’re particularly rigid, I go as far as to get them wet before the first wash. Once they’ve started softening up, anything goes: I think slightly harsher washes help with the good sort of marbling and don’t have any real downsides.