Even with zero customization, just using it for a Kanban board is incredibly slow and frustrating. My 2-person team was using the free version of Target Process

Even with zero customization, just using it for a Kanban board is incredibly slow and frustrating. My 2-person team was using the free version of Target Process and needed to migrate to something else since we hit the entity limit, so we went with Jira because it seemed like the industry standard. What we got was the slowest initial page load and slowest interactions of any webapp I've ever used. After struggling along for 2-3 months, we moved over to Clubhouse (now called Shortcut) and the difference in speed and overall experience is night and day.