Jira may be over-engineered, but I don't think it lacks anything. You can always get a plugin if something is missing. Our corpo Jira crawled because of a stupendous amount of plugins (close to a thousand). Once we had a Jira clean-up operation done, it became magically fast.
Huh - that seems a very basic missing feature in the cloud version. We use bog-standard self-hosted JIRA and markdown editing is basic working functionality. People also add mermaid diagrams/charts to the issue. As well as custom diagram plugins, excel sheets and a whole gamut of documents.
