Enshittification is specifically how something inevitably gets worse and more anti-user due to pressures from capitalism/shareholders/profit incentive.
Rot, at least in my mind, is not that specific. It could mean the codebase is not well maintained and slowly failing, as an example.
Cory Doctorow actually coined the term, so a decent strategy given how poorly it’s used would be to trust its use any time you read him and substitute it every other time
Corporate rot sounds better than just rot as enshittification happens on purpose due to seeking to extract maximum value from something where as rot is just a natural consequence of atrophy over time