In my view, if blocking is necessary, whitelisting is generally more effective than blacklisting. And if whitelisting isn't feasible, this might be a poor solution.

On the other hand, tools like Cloudflare and Anubis can create serous accessibility issues; some more than others.

I prefer rate limiting; it's elegant and avoids accessibility problems. For temporary issues, short-term IP bans can also work well.

Personally, I use fail2ban to parse HTTP logs and temporarily ban IPs for N hours if they request forbidden URLs (e.g., those blocked by robots.txt or paths like wp-login.php). Same if a IP trigger the rate limit much to often. And currently, I'm testing Anubis on my Git web UI.