When I tested the new editor some time ago, it seemed to share Visual Editor's often atrocious loading times... which are upwards of 40 seconds on many articles. The current wikitext editor loads even the largest page with almost no noticeable delay.
It appears the goal is for the new editor to eventually become the default wikitext editor. I believe the community will consider this sort of load time to be an unacceptable degradation of the current editing experience, both for new editors and experienced editors.
This should be categorized as an "actionable blocker". Loading times need to be roughly comparable to the current wikitext editor, even on large complex pages, before it is considered suitable for anything other than fringe opt-in usage.