I don't have anything against tagging and I don't think anything I've said or done supports that claim. I'd be curious to hear what your definition of "proper" tagging is, though. And I think that is perhaps what you picked up on when I speak about tagging, rather than any inherent problem with tagging itself.

So what is proper tagging then? To me, it comes down to what is the purpose of tags? Tags function to a) allow people to find what they're looking for, and b) allow people to exclude what they are NOT looking for. Tagging fandom and pairing are standard now, but there's a lot more you can tag. Setting, theme, various sex acts. If I write a fic with anal sex should it be tagged "anal sex"? Should every sex act be tagged? Some would say yes, some would say only when necessary, but what is necessary? In some fandoms it's the norm to tag top and bottom, and this tends to be the one that gets people most up in arms, it's not something that's universally done across fandoms.

AO3 only requires that the four major warnings (MCD, underage, rape, graphic descriptions of violence) be tagged, and even then authors can choose not to warn. So in one sense, as long as you've indicated which if any major warnings apply, or have chosen not to warn, then you've tagged properly. The rest comes down to fandom practice and convention which is something that, despite what a lot of people claim, varies widely.

I think the question a lot of people who feel strongly about tagging ask is, "well, why not do it?" And I think a lot of people who don't feel strongly will simply do that. Personally, I have no real desire to tag top/bottom but sometimes I do because that's what the fandom generally prefers. That said, there are plenty of reasons why an author might not tag for that, anything from spoilers to preference. An author may not want their fic to come up in searches! They just might not feel like it, and all that is fine. There are so many fics out there that ARE tagged to your specifications that you can just stick to those and ignore the ones that aren't.

I think that really hits on what I find frustrating about all kinds of tagging discourse. Firstly, it's mostly revisionist about fandom practices, but secondly it reeks of reader entitlement. There are so many fics that are tagged. Excessively tagged, even. Read the ones that have the tags you want, avoid the rest. It would be that easy. But you act like you're entitled to dictate how authors act and tag their own fucking fics. Just read the ones that are tagged! That is just as easy.

Btw I know this wasn't asked in good faith but I enjoy talking about this kind of thing, which is why I've chosen to answer.