90%+ tokens held by insiders or devs: Obvious exit trap.
Unfortunately you'll encounter a lot of coin that have 90% of token going into the dev and insiders hand.
Most of altcoin these days only allocate 5% or so for TGE and it's really low if you think about it.
Basically all of them is damn near to a private blockchain. That's why I don't really invest into new altcoin these days, all of them are just exit trap.