SQRL is a half measure, like SMS-TOTP it barely raises the bar because it doesn't solve a key real problem we actually see happening in the wild and so that would just happen more.
If site A is protected by SQRL, and I'm a bad guy, I can just live phish sign-ins for site A using SQRL from my phishing site, site B. The users all believe (as with other phishing attacks) that they're being asked for credentials by a legitimate site and so they provide them with SQRL, and I'm in.
This (very common and fully automatable) trick doens't work on WebAuthn, completely defeating phishing. This is because the fundamental idea in phishing is "Humans are idiots, fool the human into mistaking site A for site B". In WebAuthn the credentials are mechanically derived from the site you're on, so for site A they will always be site A credentials, and for site B, site B credentials. Convincing page design, an urgent email "from the boss", clever use of IDNs to fake the URL, those fool the human but not the machine, and the human is taken out of the "what site is this?" decision by WebAuthn.
But the human is left _in_ the loop in another way that leverages our strengths. WebAuthn requires a physical interaction, typically a button press by the human. So a hypothetical attack that takes say, 50 million authentications, cannot work because the human will not press the button 50 million times while you do the attack. They'll get sick of it and go on Twitter to moan instead.