I really want to see a Jira competitor succeed, it's healthy to have some competition. But it's hard to find something that competes on the per-user price of Jira Software On-Premise. (Jira Cloud is a different story...too many reports of slowness, too many UI/UX changes, too many powerful add-ons do not work on Cloud).
Next, you have to be the system of record for a company. To do that, everyone needs a license. Jira has a foot-hold because it is used for developers and for every other facet of a business (basically all company ticketing).
Although Jira sacrificed ease-of-use by offering customization, it's also what allows orgs to skip buying other tools.
Jira Cloud & Jira Server (on-premise) are two different beasts. I can speak for on-premise only. On my on-premise system which is located on the other coast of the country, a ticket loads in 1.5 ~ 2.5 seconds once your assets are cached at least once by your browser.
Things I've seen that can adversely affect your speed: installing random plugins that are poorly written, integrations, having too many admins over-complicating the Jira configuration.
Learn the keyboard shortcuts to speed up your basic operations.
Next, you have to be the system of record for a company. To do that, everyone needs a license. Jira has a foot-hold because it is used for developers and for every other facet of a business (basically all company ticketing).
Although Jira sacrificed ease-of-use by offering customization, it's also what allows orgs to skip buying other tools.