Not true - Capsicum is used by a growing amount of software, from base system utilities (like uefisign(8)) or servers (like ctld(8)) to third party stuff, like Irssi. And yes, there are language bindings as well.

The problem with Chrome is not that it’s hard to capsicumize - it’s not, it has been done and documented - but rather that the upstream developers are extremely uncooperative wrt accepting patches.