IEO now has so many good bounty campaigns and you can earn from them
IEO have no guarantee of success. Some teams participate in the IEO after the failed ICO 2017-2018. The only plus is the authority of the exchange, they have to choose the project themselves for publication and it's reputation at stake.
You said that their reputation is at risk but you also said that ieo have no guarantee ? What the ? Are you confuse ? Ieo is more guaranteed actually because the exchange reputation is at risk , binance for example but its still risky if you will invest on unkown exchanges that do ieo . so what if the ico teams have failed and migrated on ieo ? There is no problem with that . maybe they the reason why they failed is because they lack of investors and not the other way around .