It is not a protected term so anybody can use it. There will be some good ones and some bad ones. In my experience they fall into three catagories.
Professionals who have left an industry and set themselves up as expert advisers. I’ve met some very good ones. They are usually worthwile as companies contract them in to help in areas where they have no experience.
Somebody wanting to sound more important and so puts it in their job title. Often useless if they don’t have the skill, knowledge and experience to back it up.
Those employed by consultancy firms – Accenture, Mckinsey, and large companies with consultancy arms like the big 4 and IT companies. Can be ok although they take on graduates straight out of university and charge them out at ludicrous rates normally.
See also, drirector, engineer, nutritionist etc. for other non proteceted terms.