I think advisers play very important roles...they should give good advice on everything about the project: marketing strategy, project development processes, short term and long term goals, etc.
These are the basic roles where advisors should really do but some or most of them arent competent on the job that they do work for.Ive seen lots of ICO's where advisors dont really have relevant experience but still some do able to give significant purpose of such project but if i were to say its not really necessary to have these people but rather have an experienced team would really be just enough.