Seems like Twitter is 'moving fast and breaking things' as they are talking about allowing long form content on the site. (4,000 characters I believe.) This will certainly hurt Medium and Mastodon.

Meanwhile Medium is 'moving slow and breaking their own platform'. The platform has been extremely buggy recently. Pictures do not load on the PC version of the site. I've been waiting for this to be fixed for months now before posting picture heavy posts. I've given up on Medium fixing the platform. Instead of innovating (or just maintaining) their platform, they are sending people to other platforms.