IPA: /ˌɑb.səˈliːt.nəs/
KK: /ɑbˈsɔlɪtnəs/
The quality or state of being outdated or no longer in use.
The obsoleteness of the technology made it difficult for the company to compete.
Obsoleteness is formed from "obsolescere" (meaning to fall into disuse) and the suffix "-ness" (meaning the state of being). The word refers to the state of being outdated or no longer in use.
Think of something that is 'falling into disuse' — that's what obsoleteness means, the state of being outdated.