Lojban has a central planning committee, the BPFK, so there is no danger of "Proper Lojban" falling prey to this, although certainly there have been dialects of Lojban in the past which deliberately were not parseable. They don't last long; none of the Lojban tools work with their experiments, so network effects tend to keep unparseable dialects from becoming popular.

From the beginning, Lojban's design has included this feature. It would be pointless to learn as a language if you intend to extend it in that way.

There are, of course, ways to experimentally extend the language grammatically, as well as a process for changing the grammar, which has happened before via the BPFK. It evolves, but with planning and consideration.