If this issue is considered annoying by most users - then admins need to solve it immediately.
I don't think there's anything theymos can do:
The Internet is seriously flawed if everyone needs to huddle behind these huge centralized anti-DDoS companies in order to survive...
I assume Cloudflare does this to mitigate a DDOS. That leaves 2 options: no forum access at all, or an annoying Cloudflare page before accessing the site.