Like any other detection system you will always have determined adversaries that put in the work to bypass it.
But that doesn't mean you shouldn't still try to block the much larger number of less sophisticated/resourced adversaries that are using OOTB libraries and low-effort setups.
Sure, but of course since there's profit to be made defeating these systems once someone makes a program to defeat detection they'll sell it. Complicated attacks only stop simple attackers until a sophisticated attacker scripts & sells the exploit. Not that you shouldn't try, just don't expect defenses to last long-term.
are you sure it's non trivial? they posted a 2d image of what it looks like. a fairly simple model of the users wrist and mouse position doesn't seem crazy hard but the devil is in the details
Naturally it depends on how well Cloudflare built this implementation. In the abstract, though, a sufficiently accurate prediction system should expect to recover the causal structure of the phenomenon it is attempting to predict, and thus an imitator hoping to defeat the predictor should expect to contain the same causal structure (i.e. physical simulation of a human hand to arbitrary level of detail).