Bitcoin also uses a DAG (albeit in a trivial sense), so umm?
Skimming through the info on the tangle, concentrating on its dagness seems superficial (is it even one? They talk about merging nodes a lot which sounds like cycles to me EDIT: ignore this aside). Anyways, things like this should have security proofs (or at least arguments) and maybe it does, i havent read enough in depth to know. But if it doesn't i would say the skepticism is very well warranted
It doesn't matter. IOTA isn't a cryptocurrency, but a decentralized messaging platform. Coin is a funding mechanism, it's more like matrix.org on financial steroids, rather than bitcoin.
Iota also relies on a central server[2]. So many others[3] have criticized it too.
[1] https://medium.com/@neha/cryptographic-vulnerabilities-in-io...
[2] https://domschiener.gitbooks.io/iota-guide/content/chapter1/...
[3] https://medium.com/@thedrbits/why-i-also-find-iota-deeply-al...