Per my post on Reddit:
https://www.reddit.com/r/NintendoSwitch/comments/8u3dri/its_been_almost_a_week_with_the_new_minecraft/

When trying to download a texture pack that you have not downloaded from the settings previously, it is taking a long time to download, and often times out. I had an issue where my download errored out and it corrupted the texture pack. I backed out to the main menu and downloaded the texture pack from there, but it seems like the world I was connecting to still went to load the corrupt pack and not the correctly downloaded pack from the menu.  So that meant I had to delete my data for my ID on the Switch for Minecraft and start over. So the delay ended up corrupting the texture pack and there was no way to verify it and have it re-download or remove the texture pack downloaded from a host.