Doesn't that require the active cooperation of bad actors? Sure, you can create a filter to hide all posts tagged with "epilepsy-trigger", but that doesn't help if the poster deliberately omits that tag. Allowing users to tag other people's posts patches this issue, but opens up the system for abuse by incorrect tagging. (E.g. Queer-friendly posters being flagged and demonetized after being maliciously tagged as "sexual content".)
At some point, there needs to be trusted moderation.