There are lots of reasons why low adhesion is more pronounced nowadays. As a Southerner, one that that strikes me as a backwards step is that the old slam-door EMUs had soft-iron brake blocks which gripped the running surface of the wheel. This action actually scraped the wheel clean of mulch build-up as you went along, so that the rim never got heavily contaminated.
Modern stock is not nearly as good; disc brakes only operate on the face or rear of the wheel, and dynamic brakes don't have contact at all. Cosequently a modern train can slide even when the rail surface is clean - it's the wheel that's become contaminated. This can really catch drivers out if they're carefully watching the railhead and assume all is well because the rail is shiny.