The article surprised me a bit since MMM seems more like an environmentalist (or close to it) at heart, but his dietary choices don't reflect that because he's bought into the protein myth.
https://www.vox.com/2014/7/2/5865109/study-going-vegetarian-could-cut-your-food-carbon-footprint-in-half
http://www.pcrm.org/health/diets/vsk/vegetarian-starter-kit-protein
He also hasn't bought into the vegan myth, and "don't let the perfect be the enemy of the good enough" or the "black/white" thing.
Considering the fairly detailed analysis he did, and has done in the past, I'm going to go with this:
1. He knows what works for his body. He's discussed this before, how he feels better on a more Paleo-ish diet.
2. He recognizes that "less meat" is good enough.
I realize that a lot of people like the "black/white" and "right/wrong" (about any topic under the sun) because...it's easy. It doesn't require a whole lot of thought, or empathy, or the ability to understand others and put yourself in their position. That doesn't make it right though. If you're happy on a vegan diet, have at it. If you want to save the planet you'd be MUCH better off staying away from extremism and convincing the vast majority of moderates to decrease their meat intake. Or to source it responsibly.
It sounds really boring to eat the same thing day in and day out. Eating a varied diet is one of the last luxuries I think I'd give up. It also works well with eating seasonally because just when you start to get tired of a food, it goes out of season and another one comes in.
Those who do eat the same thing every day, how do you not get bored?
It would be more interesting if he detailed what Mrs. MM generally ate.
You get used to it. I make 2 things a weekend and we repeat, and someone recently told me that that's a horrible thing to do to my kids. Why? It's healthy, and it's food. We eat seasonally - but I eat salad for lunch every day. In the winter, it's a lot of lettuce and kale, with oranges and a parsley garlic vinaigrette. This week: with beets and goat cheese. In the summer? Mostly cucumber/ tomato salads.
Why does food have to be exciting?
Don't get me wrong. I like food. I like to cook. But decades ago I was fat. Why was I fat? Well, I ate too much. One of the things was - I loved food. I loved homemade burritos. I loved homemade pizza. Then I realized...I needed to stop looking at each meal as if it was my last. I can eat burritos every day. Or pizza every day. I don't need to eat half a pizza - a slice is fine. I can taste it again tomorrow!
I think that I was in the same place as you, wanting food to be interesting, when I was in my 20s. So I ate out a lot - that's how I got variety! Sandwiches, burritos, stir-fry, Indian, middle eastern. You hear it all the time from people who eat out a lot because carrying your lunch is "boring". Well, when I was a kid I ate cereal for breakfast and a sandwich with fruit for lunch every damn day. It's just food! I make sure it's tasty.
I still get bored, but a part of that is because I'm the one who takes on the mental load of what to cook each week. And sometimes, all I can manage is "spaghetti with meatballs or mac and cheese or beans and rice, you pick!"