Is this a UC-secure commitment scheme in the ROM?
No, your construction is insecure, specifically it fails to be hiding. A receiver who has a guess of $M$ can simply check whether $H(M)=c$ since $H$ is public. You can see that your suggested simulation strategy fails when the adversary has already queried $H$ on $M$ before the simulator learns that the commitment should hold $M$. The argument to $H$ should have high entropy even conditioned on a correct guess of $M$. Change the construction to $H(M\|r)$ for long random $r$ and you have the standard folklore commitment in the random oracle model.
Naively using a random oracle in the UC model is kind of like cheating. You get a totally independent random oracle for each protocol instance. It's not a great model for a supposedly public object. Those papers you reference try to use a random oracle in a less "cheaty" way, so their protocols have to work harder. Also at least the first paper avoids having the simulator program the oracle's outputs (non-programmable random oracle model) which is often seen as more palatable.