No, Jira loading is relatively OK and on par with other SPAs. It's got a CTRL+SHIFT+P style actions menu for tickets which helps cut down on point and click pain (especially for linking issues etc). Setting up statues and workflows and how they map to a board is relatively straightforward.
There are lots of things where Jira falls short, but the pain points on an under-resourced self hosted instance of ten years ago are nothing like the ones you'll find on Jira cloud today.
Does Jira still have multiple flavours of markdown for different fields and editors? Last I used it, it used a different flavour for creating and editing a ticket. Also another flavour for bitbucket. None of these were compatible and it would convert between them in the backend but I was left confused every time when I would have to switch formatting styles
I remember that from a while back, and getting annoyed - it doesn't appear to be something that annoys me at the moment so it might have been fixed, but on reflection I tend to just use the default rich text editor now.
It takes markdownish input but converts it to rich text as you type - so asterisk-space starts a bullet point list, etc.
I actually can't remember if it has a dedicated markdown mode anymore; the rich text editing supports the usual shortcuts that mean I tend to stick with it.
There are lots of things where Jira falls short, but the pain points on an under-resourced self hosted instance of ten years ago are nothing like the ones you'll find on Jira cloud today.