To this day, it remains rate-limited for people who don't have an account. Also, that fact that you (and most people) keep calling it "Twitter" is proof that the name change was an absolutely horrible idea.
For me I can't stand that the new name usurps the oldschool X windows logo and name.
Basically, Twitter is sustainable now because so much of its user base migrated away.
I have been unable to locate anything even remotely reliable other than the AMARS[0] report that shows that between August 2023 (two months before Musk) and July 2024 the EU user base dropped from 111M to 106M. That hardly seems like load shedding to reach sustainability.
I would like to see global and up to date data, but it does not seem to exist in public.