"So when you visit HTTPS sites, anyone along the communication path - from your ISP to the Internet backbone provider to the site's hosting provider - can see their domain names (e.g. wikipedia.org) and when you visit them."

Except wikipedia.org does not require SNI.

Most HTTPS sites do not require SNI.

Not every client sends SNI by default. OpenSSL's s_client does not. There are others.

    printf "GET /wiki/MediaWiki HTTP/1.1\r\nHost: en.wikipedia.org\r\nConnection: close\r\n\r\n"|openssl s_client -showcerts -connect mediawiki.org:443 -ign_eof

Some sites "require" SNI, but then do not check it against the Host header. A client can send any SNI.

    The server certificate says *.wikipedia.org.  

But there are numerous websites sharing the IP addresses for wikipedia.org, not all of them serving Wikipedia content. One example is mediawiki.org.

What if a website padded all its pages to be the same size.