Just because vegetables, lentils or nuts contain protein it doesn't mean it's the same/equivalent to the protein in an animal product.
Meat is actually super easy for humans to digest and it has no downsides to it. All vegetables on the other side contain plenty of anti-nutrients such as folate and oxalates.
Everything in human body, skin, connective tissues, tendons, hair, nails, muscles is essentially built out of protein and collagen. Fats are essential for hormone function.
Red meat has been linked to cardiovascular disease https://academic.oup.com/eurheartj/article/44/28/2626/718873... https://www.tandfonline.com/doi/full/10.1080/10408398.2021.1... etc
Unprocessed meat is what humans what have been eating for hundreds of thousand of years.
Meat products are commercial new inventions and contain stuff like preservatives, volume expanders, flavor enhancers and coloring agents. They also typically contain added sugars, sodium, malto dextrin, corn syrup.
One can't seriously put these together and call them the same, make a study where participants might be eating SPAM and then conclude that "red meat is bad".
Given the choice between "Domino's vegetarian pizza", "IKEAs meatballs" and "steak that is fried,salted and peppered" which one do you think will be the healthiest option?