I have never trusted any local ISP. They’re commonly expressly allowed by law to share roughly whatever they like about you†, and they are known to do so.
Cloudflare has at least promised not to be evil, and is to be audited annually concerning it. If they desire to be evil I have no doubt they could wangle it, but I still trust them way more than I trust any ISP, because they’re already known to be evil under these definitions.
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† (This is a gross simplification, but it’s broadly true enough in most countries.)