That's true, but then a focus on more metrics like citation counts and download counts seems like it'll just increase the strength of those journals, not underm

That's true, but then a focus on more metrics like citation counts and download counts seems like it'll just increase the strength of those journals, not undermine it. People will try to publish in Nature or Science to get attention for their paper, because those journals are widely read, and have good connections with journalists who'll further publicize your paper, making it easier to improve your metrics.