Disadvantages

Malbolge is esoteric language. It was created as a joke. There are a few so-called Brainfuck hackers around, but being honest, You can't earn a living programming in Malbolge these times.

Malbolge is way too impractical to be using language in real-world cases (even more than Brainfuck!). Developers would cost way too much and work really inefficiently. Albeit low abstraction level, Malbolge is memory and CPU time inefficient, so it's not very viable to write anything in bare Malbolge and you'd be better off by using some other language.

Finally, the language is really bounded - I/O is limited to console input and output, greatly reducing usability.