That's a fair assessment - although Rime of the Frostmaiden takes place just north of the coloured region (the ten towns aren't really on that map at all.)

Of course, one of the advantages of this is that you have a vast amount of "undefined" space to grow your campaign into if you want to make something up. Need to set your game in a kingdom with a monarch and political dealings? Why not Cormyr or Sembia? It's not like there's any published materials on what's been going on there in the last 200 years. Want a place where the Zhentharim are in charge and the local towns and villages are under the control of warring mercenary groups? How about the north Moonsea area, where Zenthil Keep is? Want to convert your game to a steampunk campaign without leaving Forgotten Realms? Boy do I have boat tickets to Lantan that you would love.

While none of this stuff has recent lore, the Forgotten Realms wiki has some surface level detail for everywhere, mostly cribbed from older editions. It's a really good resource if you want to take your campaign somewhere more exploratory, just have a read of what was there, and build your campaign ideas on top of it. Works a treat I think.