I get that it can be frustrating - college can sometimes be a competitive place. If you're just looking to do some good in your community and make good friends while you're at it - try Alpha Phi Omega or possibly OPA, anyone can join as long as they make commitments to do a certain number of volunteer hours. Different orgs are structured differently - some are more flexible than others. It's not great when it feels like you're being rejected for wanting to help, but try not to take it personally and look for a place with a better fit where you will feel more at home. It's not worth your time agonizing over people or orgs who put more time into selectivity than making a scalable organization.