These crochet mitten patterns for children are from 1916 and 1946. Would these look out of place in a book published today? Is it because they are classic, timeless designs? If you click the photos, the links will take you to websites that have the magazines these photos came from in more detail and I think you'll agree, most of the patterns in them would fit right into a Debbie Bliss or Lucinda Guy collection, so "classic" is accurate. I also think that crochet mitten patterns haven't changed much in almost a century. Crochet mitten patterns for colorwork beyond stripes and variegated/self-striping yarns are few. Danielle Kassner's Crochet Codex jaquard crochet mitts, mittens and cuffs patterns, for example, are exceptional, and arguably would stand out even if colorwork crochet mittens were more common. Still, part of what makes them exceptional is that they are, really, an exception to the standard. While one of the reasons is likely because crochet colorwork can make a very thick, stiff fabric, there are other approaches, including embroidery and appliqué, that can be used to add color and detail without too much bulk.
Pet peeve moment: the number of patterns for mittens/gloves that are just tubes with slits for thumbs suggests to me that we don't need any more of those (especially ones where the fabric is so thick it looks almost like you are wearing chopped-up oven mitts). Gussets and actual thumbs are not terribly difficult. Of course, that there are so many patterns available also suggests that they are popular and a lot of crocheters like to make them, so take that with a grain of salt.