"learn the ropes on black and white film, and only then move into color"

Actually, this was because developing color prints is orders of magnitude more difficult than B&W prints. Most of your famous early photographers are known for what they did in the dark room, not for their composition skills. E.g. you can buy an Ansel Adams poster for a few dollars, but an actual Ansel Adams print will run you several thousand.

I haven't seen any material since the digital age took over (sometime around 2000) recommend that photographers start with B&W.

I would still recommend that people start with black and white pictures, or at least spend some serious time on it sometime early in studying to make photographs. Darkroom skills per se have little to do with it. I would also recommend that aspiring painters spend some time making black and white photos, charcoal drawings, or the like.

Learning to see and think about the lightness relationships in a picture is a very valuable skill for color photography which is easier to learn when trying to make black and white pictures because there are fewer distractions and fewer choices to make.

> I haven't seen any material since the digital age took over recommend that photographers start with B&W.

I am not super familiar with recent introductory photo courses/books/etc. Have you examined many of those?

Yes, all of your more traditional mediums will start with black and white for the same reason that color is vastly more complex. No one should start to paint in color until they've got a good foundation on just getting shapes correct.

While I haven't taken any formal classes in photography, I started learning around 2000 which is about the time digital started taking over. I started with film, then quickly moved to digital. None of the digital materials I used ever recommended starting with B&W. And the more formal classes I've looked at (but not taken) don't appear to start with B&W either. At the very least, they cover a lot of color stuff, where the older film classes only covered B&W, color was considered very advanced.

I honestly think B&W photography is actually harder than color when talking digital. That's because the scene you see has color in it, and it can be tough to imagine what shapes will be dominant when converted to B&W.

Not only this, but:

When making a full color photograph, it is often (though not always) most effective to get the lightness right first, then worry about hue/chroma afterward.

Sometimes it is helpful to hide the color altogether and look at lightness alone while producing a black and white picture which looks good as a black and white picture, then work on the full color version afterward.