> I liked the idea when they just showed images of words that an OCR couldn't read accurately.

Like I said, popular spamming software like Xrumer could crack those captchas ten years ago.

> And no, I disagree that we have no option but to rely on "centralised" services like cloudfare or Google.

Can you pitch alternatives, though? For example, an attacker can still spoof IP addresses in 2019 and create volumetric attacks that you certainly cannot endure without someone's help upstream (i.e. centralization). No need to bother with spoofing though since you can rent a botnet for peanuts. Attackers have decentralized attacks but there is increasingly only centralized defense.