I thought TLSv1.3 already encrypted the SNI?

No. ESNI is an later-created extension to TLS 1.3

It does

ESNI is not implemented yet on any website. And there is no software support except beta versions of Chrome/Edge and you have to manually toggle flags in dev mode.

All SNIs are passed as plain text to your ISP/VPN, even with DoH/TLS secure DNS enabled.