Consider that if a Django user wants to contribute with an account they're already logged into, the only thing they can see is https://github.com/django/django/pulls - a wall of structure and external references, with no clear way to suggest features. To the community's credit, people gently redirect "stray" pull requests to the proper channels, but this still has to feel like a form of rejection to well-meaning developers!
Compare this to https://github.com/facebook/react/issues and https://github.com/rails/rails/issues - inviting colors, a clear way to raise issues one click away from the codebase itself, centralized discussion of those issues, automatic links between PRs and issues. Nobody is left behind; any suggestion can become a discussion with decision-makers in place. This is what the modern developer has come to expect.
I love Django as a framework - it's a set of abstractions that make a ton of sense together, but simultaneously are much more explicit and easier to dive into than Rails. I can command-click my way through the entire stack in VS Code and know exactly what's going on; when there's a customization to make, there's almost always two or three hooks I can use to make it happen. And it pains me that there seems to be a fear of change and a fragmentation of contributor tooling that's holding it back from evolving. I don't know that Trac -> Github is the best path, but I hope that this is the first of numerous innovations that the core and board intend to discuss earnestly over the coming years.
EDIT: As I consider what I've written above, I'm thinking about a concept of TTFK - "Time To First Keystroke" that's intended as part of a contribution. Once you start writing an issue or coding a PR, assuming there's a clear path for it to get accepted, that first keypress is the start of an avalanche that gets obsessed developers deeper and deeper engaged. But if you look at the README on https://github.com/django/django , count how many clicks it takes, and words to read, and new platforms to join, until you can type your first character on a non-documentation feature request. It's not a fun number. Process/triage is great, but you have to have a way that someone's unstructured contribution can gain structure over time without requiring them to retype it or jump through hoops.