The trick is to use the most normal hardware, software and network connection you can think of. Which I assume you aren't doing for ideological reasons, which is fair.

My ISP seems to frequently rotate IPs with other people who can't behave, so my IPs always have garbage reputation... that probably has a lot to do with it as well.

How do I know this? I have received reports from various websites (and manually queried some public block lists/RBL/etc.) that my IP range was blocked due to all sorts of different things like open proxies, CSAM etc. even if I've never visited that site before, and I know just from being a neteng that that such traffic is not originating from my devices/router and I don't have any observably compromised devices or suspicious traffic when monitoring it.

This is common for third-world ISPs. Cloudflare would never block, say, Comcast, but they have no qualms about blocking the few largest ISPs in Brazil because who cares about Brazil? Those countries also have IP address shortages because we refused to move the whole internet to ipv6 yet, and may share just a few addresses per city.