As part of the devs farewell message on their site, they have included malicious code to make each visitor sends 2,000 requests to the dbzer0 servers in an attempt to DDOS and take the instance offline.
Not every admin has the time or skill to curate. As long as the dev is open about it and there are configurable features to disable it, I don’t see what the issue is. Ultimately it creates no difference for a user if the admin creates it or the Dev does as long as it’s communicated.
The advantage of the fediverse is “don’t like it, go to another instance or build your own”, not to tell devs what they can and can’t do. Hell I never even interacted with Tesseract since I use a different client and an open instance.