> If you're a professional athlete trying to be vegan, then sure, you'll end up with a weird diet

Professional athletes that are actually vegan are 4 sigma outliers. For most normal humans it's not possible to even be a more-that-casual athlete in any competitive sport eating plants. Animal meats contain more than just protein including things like iodine, creatine, vitamin D, etc. A quick google brings up numerous studies on the nutritional deficiencies of the typical vegan diet you would need to rely on external supplementation for. Keto diets and other fad diets are also not great for the competitive athlete.

If you're vegan because you don't want to eat animals there's nothing wrong with it. When the vegans start pointing to the outliers as evidence "it can be done" it's just a deep cope to make everyone as miserable as them.