I found Firefish which is a better alternative to the standard Mastodon application. It's compatible with Mastodon and has better features. It allows users to create web pages and the character limit is 3,000 instead of the 500 on Mastodon. It feels like a good limit for the type of site that it is. Plus this means that it can handle long posts from users on customized Mastodon instances.
Firefish is a fork of Misskey which predates Mastodon by 2 years. As for why one would fork Misskey into Firefish or make Mastodon, some of the rationale for that is explained in the Fork a repo page by GitHub.
You can ask the developer of Mastodon personally why he didn't just make Misskey better, or the lead developer of Firefish why they didn't just contribute to Misskey or Mastodon, but fundamentally the platforms are very different even if they're inter-operable, and this comes down to the actual design of the platforms.
I think that's good to be aware of. The Wikipedia article mentioned that the APIs are not compatible. As long is the interoperability is good I think it works well enough.