There is very little science in nutrition, despite the existence of thousands of studies. There are huge gaps in even the basics of nutrition understanding, and we are constantly discovering new confounding variables. Some dietary fibers were being counted as carbs as late as the 2000s. The huge impacts of the gut microbiome on digestion of food has barely been recognized in the last 10 years, and we still basically know nothing about it. Inter-personal variations in base metabolic rates and/or absorption of nutrients from food is gigantic, with basically no known reasons for it (some of the difference is tied to muscle mass, but even if you eliminate differences in muscle mass, there are still large differences that remain), and no inclusion in common models and dietary recommendations.

I'm not trying to say that red meat is good for you. I'm just saying we have no real idea, and you really shouldn't trust a doctor about any of this stuff any more than you should trust the latest health influencer crackpot. Try things out, see if you can eat similarly to people you know who are in good health, and get blood work done regularly to see if you're ok. Probably avoid highly synthesized foods.