Vegetarian with ADHD (among other things) here! I started the same way many years ago, by cutting out red meat and pork, and then reducing meat consumption until I realized I had been eating like a vegetarian for a week and then committing.
For me it was about what was and wasn’t doable. I struggle with motivation a lot, and bothering to cook a proper meal everyday or sit down and do proper research into what constitutes a healthy diet isn’t something I can just make myself do.
Honestly if this is about CO2 emissions, which it originally was for me, then cutting meat by 90% or whatever is almost as good as going vegetarian and will be way easier in terms of nutrition.
I live in a very small town so if I want vegetarian here we’re talking a margarita pizza or eggs on toast :P
That said I’ve mostly cut dairy out of my diet, but I don’t remember to check the ingredients of everything I eat so who knows how plant based I am these days. Probably some dairy based butter in some of the things I buy.
I have a lot of stomach issues and unfortunately react somewhat to oat milk, but almond milk (which has other climate issues to my knowledge) and coconut based milk is working very well for me.