One of the possible major problems with decaf are the extra processing steps. You're wading into "processed foods" territory.
"The most-common methods of decaffeination involve chemical solvents, usually ethyl acetate or methylene chloride. In the direct method, the coffee beans are steamed and then rinsed repeatedly with the chemical solvent to flush away the caffeine."[0]
It is not a given that the coffee doesn't have extra unhealthy chemicals or is stripped away of vital nutrients besides caffeine.
[0]https://www.britannica.com/story/how-is-coffee-decaffeinated