Jake here, and I work on the Jira team at Atlassian. Thanks for this feedback. I know historically that Jira hasn't been as performant as many users would like, and in the past year we've made some enormous improvements to close this gap!
You can read more about some of the performance improvements we've made in Jira Server here: https://www.atlassian.com/blog/jira-software/introducing-jir...
And in Jira Cloud here: https://community.atlassian.com/t5/Jira-articles/6-ways-we-v...
Any questions or concerns, or to speak further with myself and a Jira PM, please shoot me an email: jake (at) atlassian.com.