While GitHub and GitLab have dedicated design and front-end teams to improve their UI/UX, Gitea and Forgejo aren't large enough to reach that scale, even after Gitea became a company.
For example, look at the number of issues triaged with "UX" [0] or "UX Paper Cut" [1] on GitLab. It is an order of magnitude larger than you would find in any other FOSS option.
[0]: https://gitlab.com/gitlab-org/gitlab/-/issues/?label_name%5B...
[1]: https://gitlab.com/gitlab-org/gitlab/-/issues/?label_name%5B...