Look an obvious first step against this insanity is to at least act proportionately: block only those IPs that *have* been a source of too large a problem to be dealt in other ways, do so only for a limited time (it might be an incremental increase, maybe beginning even with just few hours, up to maybe 6 months), and *use more proportionate measures when they (still) might be enough*, such as the slow-down or delays that others proposed, and even those in incremental increases.
And where there's no unwieldy problem, just do nothing (other than reverting the damage).

Just a few weeks ago I was pondering how bewilderingly "not badly" Wikipedia works in practice, despite his debatable mantra of allowing immediate modifications from anonymous persons.
Please don't ruin it, unless you have very good comprehensive alternatives.

Kind regards,
Gabriele