If you just want an issue tracker, there are many options. Bugzilla, Mantis, GitHub, GitLab, Gitea,... Some of them customizable via plugins. Heck, you can even do it with Excel, I don't recommend it, but it gets the work done at many places. I mean, it is just a shared TODO list.
But then you want people to get notified by email, and the boss want a colorful dashboard with progress graphs, and QA wants a documented process, and developers want to attach tickets to their commits, project managers want time estimates, customers want to report bugs, sales want to send invoices, etc... That's how you get monsters like Jira, because the organization itself is a monster.