I like a nice quiet lunch to get out of sun and crowds. They took my favorite away, which was Trail's End, and the weekend brunch buffet isn't as quiet. I've replaced it with Whispering Canyon, the boat ride is a nice way to relax.
Other favorites:
Grand Floridian Café
Le Celier (dark is nice)
Chefs de France (not quiet, but I like pretending I'm on a sidewalk in Paris)
I've only done San Angel Inn for dinner, but lunch would be good too
Liberty Tree (followed by parade, then Hall of Presidents if it ever reopens...that's like 3 hours of sitting, an excellent midday break!)
SciFi (a little on the loud side)
last year at food and wine when I needed a break from the crowds, I stepped into the beach club and grabbed a soda from their quick service and hung out in their solarium, even though I wasn't a guest there! It was quite serene.