There seem to be two different issues being raised here.
1)
Attack of the Clones. Personally I'm not bothered about increasing numbers of Thoth clones. Everything gets imitated at one point or another. But as long as the original is still available it's no big deal.
Plus it's not altogether clear what exactly constitutes a Thoth clone. To me a clone is a deck that is based, more or less, on the visual style of the original. It's just a cheap knock-off.
But some people when they say Thoth clone or Thoth inspired, what they actually mean is Golden Dawn based. Ever since I joined this site I've been baffled by comments like, "the Haindl is a Thoth inspired deck". It is? Well it's news to me. It might share the same structure as the Thoth, but that structure is not unique to the Thoth. It's Golden Dawn. The Thoth Tarot is a Golden Dawn deck.
Take a look at the Aeclectic decks section. Why is the Via Tarot listed as a Thoth clone? The artwork is nothing like the Thoth.
Take a look in the "Thoth Inspired" section. How the hell any of those decks are inspired by the Thoth is a complete mystery to me. It should be called, Based on the Golden Dawn Tarot model.
2)
Invasion of the Body Snatchers.
This is one of the more insidious attacks on the Thoth. Not content with merely copying, these people wish to claim the Thoth for their own purposes. They like the art, but they don't like the ideas and inspiration behind the art. Why? The ideas are deep, difficult, and require a degree of honest effort to even begin to get to grips with them. The New Age does not like this. "Deep" is too complicated. Shallow and no substance is better and easier. "Difficult" is too un-inclusive for the New Age and elitist as well because morons feel left out. "Effort" sounds too much like hard work. Why bother when you can be spoon fed some easily digestible slop that's makes you feel all warm and fuzy inside. Awww.
Also there's Aleister Crowley.
While a castrated Thoth deck may be amenable to assimilation into the New Age collective, Crowley is not. Quite simply Crowley is too dangerous and disturbing for the New Age to handle. He is not the typical meek and mild, white light guru favoured by the timid and fainthearted. On the contrary, he's challenging, provocative, and controversial. To the New Ager's there is only one remedy. Get rid of him!
(Un)fortunately interest in Crowley in on the rise. Instead of being intimidated by the scare stories peddled by the ignorant and uninformed, growing numbers of people are having a look for themselves, and they are often surprised by what they find.
While Crowley's reputation my have been damaging during his life, it has been the saving grace of the Thoth and will be for quite a while yet.