1. At a point, Medium stopped adding value to blog posts and their network, to the point that they had to strongarm some of the larger networks to try and stay on their platform (e.g. FreeCodeCamp) and failed. Currently, Medium's best value proposition is long-tail SEO which just encourages more low-quality content.
2. In general, the long-form content landscape has shifted more toward short-form content in terms of things like Twitter and TikTok. Even Substack, which is a reasonable Medium alternative and superior if trying to build a readerbase, hasn't received as much buzz as it did years ago.