Yes they are, but their cultures can still inspire eachother. Thaylens are traders, and travel all over Roshar. We have seen them in both Shinovar and Kharbranth, as well as on the Shattered Plains. They are most likely selling stuff in Iri as well.
We also have the fact that the Irali seeks knowledge. They might have borrowed the Tidereader from the Thaylens. It wouldn't be far-fetched to assume that Thaylens have similar things to a Tidereader either. They have a big fleet and live on an island, so the sea should be important.