There are so many systems out there. Right now we're also evaluating YouTrack from JetBrains and OpenProject.org (which is a fork of a fork of RedMine).
We don't want to have to move again any time soon, so while we're evaluating features we're also trying to predict stability and viability. To that end, when available, I'm including in our evaluation notes 1) when the company making the system started; 2) when the system was launched; 3) how many staff the company has.
JetBrains started in 2000, YouTrack launched in 2009, and they have over 900 employees. OpenProject launched in 2012. Both seem to be stable and under active development.
ClickUp has a lot of features and looks nice (we haven't dug into it yet). But they launched in 2017, and raised Series A funding in June 2020. So they're young. That doesn't mean they're bad. It just means they're less known, and have not proved long-term viability. On the plus side, it also means they don't have the 18 years of cruft in the system that Jira (launched in 2002) seems to have.
In my experience the right project management system can really help developers, so I always want to hear everybody's experiences, good and bad.