This means that these outdated 'Series 0' watches are no longer eligible for repair or other services at Apple Store and Apple Authorized Service Providers.

The list of obsolete models includes the first-generation Apple Watch Edition with an 18-karat gold casing, which sold for up to $17,000 in the United States...
All other 38mm and 42mm aluminum and stainless steel variants of the first-generation Apple Watch, including variants by Hermès, are now also considered obsolete.
Apple classifies a product as obsolete over seven years after the company ceased its distribution for sale. The original Apple Watch ceased production in September 2016 after the release of the Apple Watch Series 2 and Series 1 models, so the recent first-generation models have surpassed that seven-year mark.
Read more: Latest pricing information for Apple Watch Ultra 2.