The wavelength of the laser light is pretty constant for reading CDs and CDR/RWs. You don't change it at all. What is different is the wavelength for reading DVDs. It has a shorter wavelength to make it possible to pack more bits onto the disc.

What does matter is that the reflectivity of the media. A pressed CD will actually have pits pressed into it. Whilst a CDR will have dark spots burnt into the dye layer which cause the laser light to be absorbed and appear to be a pit. A CDRW works by having a special layer which can have it's state changed between one with low reflectivity and one of high reflectivity.

Some devices are very picky about the reflectivity and will refuse to work on writable media because it can't properly focus as it's not within it's threshold. As you said, manufacturers are now designing the optics to be more tolerant.