WoW communities for various populations exist on most major social media as well, including Facebook.
Saying hello to strangers isn't a bad start, but don't be surprised if no one acknowledges your presence. You may have better luck in dungeons you run using the LFG tool, particularly if you fall into a group that elects to run several in a row. A far better method is getting involved with communities both in and out of the game. For one, the World of Warcraft subreddit is a fun place to hang out. They have a great list of Discord servers you can join for specific classes or interests related to WoW, as well as an official Discord server of their own. WoW communities for various populations exist on most major social media as well, including Facebook.