It is impossible that all ICOs are a scam, if so, months ago we would be without new altcoins, when instead alts market is growing every week, what happens is that many ICOs are mismanaged or poorly developed, which causes the collapse and end up defrauding their investors.
Yes, poorly developed or unrealistic roadmap. They have no developers , they hire later after ICO sales. Yes, some of them only know the knowledge of blockchain tech but not real developers of this technology. if they are succesful raise money then recruit developers if not the project will die.