Well, I did a comparison of the OS on both machines, and there are differences. The biggest one I can find is Windows Home versus Windows Enterprise. But it seems silly that such a feature would be limited in such a way. See the attached image.
To me it should be a no-brainer to enable drag and drop on all editions/versions of Windows 11 if it previously existed on all editions/versions of Windows 10. Am I wrong?
The edition of Windows (Home, Pro, Enterprise, etc.) makes no difference. The build revision is what matters in regards to Explorer features.
You're Enterprise version is old (build revision 2777). IIRC, build revision 3007 and higher have the new Explorer. Your old Enterprise build is running the older Windows 11 Explorer (i.e. the one that's less crippled).
As of build 3007 (or thereabouts) Microsoft updated Explorer to use their latest development tools. This makes things easier for them going forward and probably makes it easier to support the latest high dpi screens, provide better dark mode support, and other stuff that's mainly cosmetic. In doing so, they dropped some features that many users have come to depend on. Presumably the features would have been retained if it were easy to do so, but Microsoft says very little when they remove features, so we're left to speculate.
We can, and should, continue to complain about the removal of useful features and push for their return.
In the meantime, some users are working around the issue by uninstalling and blocking updates (not a great strategy IMO) or installing various patches that roll back to the older Windows 11 Explorer or the Windows 10 Explorer, as those code bases are still in the OS. Such patching is not for everyone (or can't be done in the case of managed company-owned computers). Patching usually works fine for home users (especially the more technically savvy), but there is always the potential for issues in the future.
I think Microsoft has the talent to give the current Explorer feature parity with the old version, but for whatever reason they don't seem to care about doing that. I'm not holding my breath. I'm still waiting for them to fix the feature "Also apply this template to all subfolders". That's been broken in Windows 11 since January 2022.