I've been experiencing this issue for awhile now and it renders the Marketplace unusable and the Profile barely functional. I've reproduced the issue on a Switch and a Switch Lite. I don't suspect it's an issue with my network since other online functionality on the Switch works as expected.

For me to reproduce, I only need to visit the Marketplace. It doesn't seem to make any difference if I'm signed in/out of my Microsoft account.

The attached images show what I see regardless of how long I wait around. The asynchronous data never loads to replace the loading animation for pictures, names of categories show their variable names rather than whatever value should be assigned to them, but some data is there... like the names of items, price, etc. For the profile, some stuff (e.g. hair styles) appears, but other items never do.

If you need more information let me know. Hope this helps.