Does IN Player Upsampling Benefit Older CDs More Than Newer CDs?

Based on my own experiments, it's not the age of the recording, it's the age of the DAC.

New DAC's perform much better with plain Redbook than old dacs, but still may show slightly more sparkle with upsampling.

Older '80s (bought in the '80s) CDs sometimes benefit from engaging De-Emphasis if you have the facility on your player or DAC, because they can sound muddy compared to more recent CDs.

Otherwise there is no hard and fast rule it's all down to personal taste. Personally I don't use up-sampling but I have found IMHO that up-sampling to DSD sounded best.