Eating a diet largely based on plants but with meat every now and then has all the benefits of a purely plant based diet but without the problems
Eating meat is a fantastic last resort if you don't have enough food and your only other option is malnutrition/starvation, but it's terrible for you as anything other than a stopgap until you can eat some plants/fungi.
After allowing for measurement error, a 3% increase in the consumption of energy intake from animal protein was associated with a 15% higher risk (95% confidence interval [CI]: 3-30%; p(trend) = 0.01) and a 2% increase in energy from plant protein intake was associated with a 23% lower risk (95% CI: 36-7%, p(trend) = 0.006).
Eating meat seems like a viable strategy for many other species, not sure why it isn't a viable one for humans as well, especially given that we seem to be highly evolved as hunters (I mean, we are, by a long shot, the most successful predator in recent evolutionary history).
Eating meat is fantastic because it contains a lot of macro and micro nutrients. With a vegan diet it is extremely hard to impossible to get all micronutrients.
2/3 of people trying to become vegetarian start eating meat again. Meat reduction simply is more viable.
Of course eating too much of this powerful food is bad for you. But also sunlight causes a variety of diseases and we don't try to live without sunlight. Obesity and cardiovascular diseases are not really an issue if you have a reduced intake of meat. Red and processed meats increase the risks of colorectal cancer with relative increases that seem really high, but with tiny absolute increases as colorectal cancer is extremely uncommon.