Just across my mind, if Alt coins or ICO listed and lower ranked exchange it's does mean they are legit ? I don't think so. I had noticed few ICO make slogan we are on exchange to attract investors. Although they don't have any team but spending small money they are listing lower rank exchange. If you are thinking they are legit due to listed on exchange than I will give you example about Bitconnect ( BCC). Do you remember it's price growth was too high ? What is current situation ? Delisted from all exchange and now it hasn't any value.
Usually an ICO try to listed an exchange hardly. Because they want to sale their hold token. Eventually they sold their all coins and skip with found. In a result token price will drop ultimately. It's called slow poison, they will scam slowly.
However before you buy any ICO or Alt coins check how they are potential. I have a
guidelines may be it will help you little.
If they listing on the low rank exchange it doesn't mean they are not legit. Do you think a scam ICO cannot list their coin in some well known exchanges ?
They could raised millions of dollars and just pay the big exchange to list their token, so it is not like that.
The only way to know the scam ICO is just by doing your research to that project.