Nothing is important enough to be worth using JIRA for. When a company or team adopts JIRA it's the universe telling you that they've given up on doing anything valuable or useful. Trying to make such a codebase better is an exercise in futility; writing TODOs is as good a way to pass the time and collect a paycheck as any other, and any vestigial useful work to be done is more likely to be tracked in TODOs than in JIRA tickets.