> There is basically no downsides to eating too much protein

A more nuanced opinion from the Harvard Medical School:

"Can too much protein be harmful?

The short answer is yes. As with most things in life, there can be too much of a good thing and if you eat too much protein, there may be a price to pay. For example, people that eat very high protein diets have a higher risk of kidney stones. Also a high protein diet that contains lots of red meat and higher amounts of saturated fat might lead to a higher risk of heart disease and colon cancer, while another high protein diet rich in plant-based proteins may not carry similar risks." [0]

[0] https://www.health.harvard.edu/diet-and-nutrition/when-it-co...