I understand, but my problem is with influencers pushing only (animal) protein without considering other dietary factors important to health.

For protein sources, a quick look online says seitan, quinoa and nuts (for vegans) and eggwhites, cottage cheese (for vegetarians) are your most efficient options looking at protein per 100 grams. If you prefer lower calorie foods, beans, green veggies and mushrooms are also good options (high protein percentage but you have to eat a lot). For a high protein diet, especially for veggie/vegans it's generally better to replace every meal with one slightly higher in protein than to try to add one foodstuff to your diet to achieve it all. For example quinoa or whole wheat options for your rice/pasta. Adding lentils to your tomato sauce and yogurt with nuts/seeds instead of cornflakes will get most people a very long way.