"Why not" doing it yourself, then?

Because I have no interest in it, nor have I expressed any. I posed a question (with my reasoning), not a criticism.

I'm actually modifying the site DOM to remove the dark patterns. There's no request for remote content that I can block in most (all?) cases. This is fundamentally different than an ad blocker. It's closer to a curated selection of grease monkey scripts

...or a greasemonkey script.

I'm definitely not installing an extension just for this.

A set of greasemonkey scripts could work but my intended audience is more casual than greasemonkey users. Having a curated set of scripts bundled into its own extension makes the marketing story and installation flow easier.

I also think the security will be better on my extension. You have to give greasemonkey edit permissions for all websites whereas I have a PR in the works where you only grant permission to the sites you want to disengage from. Even now it only asks for permissions to the subset of sites it modifies. Due to the nature of how web extension manifest permissioning works, greasemonkey can't offer this. If you look at their permission model it says "This add-on can: Access your data for all websites". IMO that's way more dangerous than your paranoia about a new extension with tight permissions.

...or a modified hosts file.