Only a suggestion can you delete a phone verification so that people can easily register? Mosly people want to play anonymously.
This is the primary reason I tend to stay away from such sites. Phone verification is basically a form of KYC verification which reveals our identities in some form or another.
There are a lot better alternatives out there who don't ask for any form of KYC and only need your username and email basically. These websites need to get rid of such KYC systems if they wish to attract more gamblers.