There is one hard wall that stops very old clients from connecting: Not supporting a new enough version of TLS. TLS 1.2 is from 2008, and TLS 1.3 is from 2018. Web browsers older than 2008 can't connect to modern websites since TLS 1.0 and 1.1 were deprecated from web servers in 2021.
TLS 1.2, the standard, may be from 2008 but support for it in browsers did not start to appear until around 2013.