[sfifs]

Well if you have an easy solution that you think would work, why don't you put up a website, commission a DDOS attack from a skilled actor and try to demonstrate mitigation?

Companies pay big money to CloudFlare. If a simpler and cheaper solution is workable, they'll pay you instead.

[SiempreViernes]

Just like telling if it's raining is easy but stopping rain once has started is hard, the claim is that it's not hard to detect if a site is being ddosed.

[beagle3]

It is not at all easy to tell the difference between a DDoS and the slashdot effect (or HN hug of death, depending on your age). At least not without a man in the loop.