Hardest part lately is not finding sites, it's finding sites that are actually alive and not just dressed up for selling links. Metrics look ok, traffic graph looks ok, then you check pages and it's 80% random guest posts about crypto, pets, loans, cbd... all on same blog lol.
For white hat stuff, response rate is the killer imo. Even when the content is decent, most site owners either ignore or ask for money straight away. I've had better luck going narrower, like small industry blogs/newsletters and resource pages where the topic fit is obvious, instead of chasing DR all day. Slower, but less junk to filter.