You're referring to the on-prem Jira. That might suck, sure. My experience has been purely using Jira Cloud and Confluence Cloud, both of which I've found to be snappy and responsive.
Cloud does not give you the flexibility of your own plugins, your own redundancy design, or your own server upgrades. On top of that, the performance is pretty variable and is far worse than a self-hosted Jira on fast hardware.
It’s interesting to me that your lack of experience to make a comparison qualifies you in some way to criticize the experience I actually have.