Look at Legacy Animation. It was marked as being “deprecated” for a decade. And then it became the Legacy Animation system, when it was finally acknowledged that there’s many, many common use cases where’s it’s vastly superior in both performance and ease of use - than all other alternatives.
This is much the same with Builtin.
Think of Builtin like that. There’s no reason to deprecate it, so it’ll become the Legacy Renderer.
Further, at the rate of actual improvements to URP, it’s not likely that URP will be able to replace Builtin for another 5 years, even if they never do a single low hanging fruit improvement to Builtin during that time.
But, much more importantly, than all of the above, Builtin is a long known quantity, with a huge array of online tips and tricks and github repos and other facilities offering improvements to both the functionality and the performance… almost none of which URP can match.
Even more importantly, you can make your game, starting today, and work on it for the next 5 years, with Builtin, and then, just before release, experiment with the new version of URP then and there… rather than trying to keep pace with URP “improvements” and build your game across that time.
If you’re starting today, use TextMesh Pro, the old input system (with Rewired if you need complexity), Builtin renderer and nothing else. You’ll iterate your way to completion in a far shorter time, stay sane and be able to consider upgrades at the point of completion in far less total time than it would have taken to keep pace with the alternative “production ready”* “features”** that don’t have the fuller features nor user insights.
*ha
**scare quotes, if you’re wondering.