In addition to the excellent points as to why these sorts of schemes don't work anyone proposing these schemes should explain why, if their scheme actually worked, wouldn't just be a way for some rogue government actor to impose a blockaid on donating to their political opponents or what not.

The whole reason preventing 'spam' in Bitcoin is hard is because Bitcoin was designed to be censorship resistant and to depend itself on censorship resistance to work, to take advantage of the nature of information being easy to spread and hard to stifle.  You don't need to settle the perennial debate on if filtering data stuffing nft shitcoin nonsense constitutes censorship itself to recognize that from a technical perspective the same *means* are used, and have similar effectiveness.

If anything ordinary transactions are more vulnerable than bullshit:  Bullshit doesn't care much about how it's encoded.  Ground into TXIDs? Stuffed into 'fake addresses', twiddling bits of signatures?  There is no end to the flexibility of bullshit encoding because the network doesn't do anything with the bullshit data.  The honest user can't so easily freely change what they're doing to avoid some filter targeting them, and they may be much less well funded than a spammer.  It's easy for a spammer to e.g. get a relationship with a miner because while although what they're doing may be unpopular and repugnant to many, it isn't *illegal* anywhere.

Now I don't fear for Bitcoin's censorship resistance, these filtering methods ultimately don't work all that well.  But their advocates argue that not working well doesn't necessarily mean doing nothing at all-- maybe pushing hard and constantly issuing updates that stamp out each use as it's discovered could at least reduce the total volume of spam.  Yes, it probably could.   But at what cost?   You've just appointed or empowered a self appointed dictator[1] over what transactions are good or not, who will now waste lots of energy squishing stuff and you'll inevitable disagree with some of their decisions.  You'll have sent a clear message to powerful actors that there exists tools to suppress transactions they don't like (or just haven't approved of) if only they apply enough pressure to node operators, developers, and/or miners.  And sure while the censorship may not be complete, they may not care just like people constantly demanding 'spam' filtering are fine with it being incomplete at best.

I've grown wary of calling this traffic spam because it result in the wrong way of thinking about it.  Spam is messages directed to you that you don't want, filtering it is largely effective because all the filtering need to do is keep it from showing up in front of you-- it's still 'effective' when your (ISPs) computer had to process the spam, it's still effective if someone *else* got the spam. It just has to keep you from seeing it.   But this traffic in bitcoin involves a consenting sender, one or more consenting receivers, and a consenting miners who happily got paid for their facilitation.  To block it effectively, it has to be blocked by pretty much everyone.  Because short of using a block explorer or something you would never even see the 'spam' at all, the criteria for success is stuff like your computer not spending time processing it (or at least not storing it in the chain)... and that is an infinitely higher bar than applies for email spam.

So I think you could fairly say that if you define spam the same way we do for email Bitcoin is already has almost perfect spam filtering,  that the only spam that remains is varrious kinds of 'dusting'.   People seldom complain about dusting though for that there are lot of additional things that could be done, because like email spam you wouldn't have to block it everywhere for everyone for it to have an impact, and because there is an involuntary receiver that doesn't want it.


[1] And inevitably the person who wants this job most is the person who on no accounts should be allowed to have it... that is even clear already in Bitcoin where the most outspoken anti-spam person is basically infamous for their fringe judgemental views.