I am a Registered Dietitian from the United States. I have had to recognize that my education and practice in the field was not immune to the effects of US food policy, which includes commodity farming and corporate influence. The Dietary Guidelines for Americans (and I’m assuming other countries) are guidelines optimized for many things, health being only one.
I think the best advice is the simplest—as many have said, you probably aren’t eating enough vegetables. You could do a lot worse than following similar diets to those who live the longest, in case there are some causal links there. The Mediterranean or Blue Zones type diets approach this.
Mark Bittman and David Katz wrote a nice article that I like on the topic: Here
Most importantly, realize our bodies are highly adaptable and there is no universally perfect diet.
Related: In Robin Dunbar Explains Humans’ Circles of Friendship—The Atlantic, Robin Dunbar says:
Source (to me): The Circles of Friendship (kottke.org)