Please. Captcha by default. Email domain filters. Auto-block federation from servers that don't respect. By default. Urgent.
And yes, to refute some comments, this publication is being upvoted by bots. A single computer was needed, not "thousands of dollars" spent.
Do not make assumptions on how other instances are operating. You don't know what measures they're taking. If they did not cause you trouble yet, don't try to predict it by making generalizations. It creates an echo chamber Internet.