If you value your experience and really like casino of your choice then registering with your email is the best idea.
There are sites where will assign you a temp username and you will be able to play.
But in case your browser will crash, you lost connection, or something will go wrong, you can lose your deposit.
It is not recommended to play with temporary accounts.
Yes, I also believe it's better to create an account. More guaranteed for gambler. Surely we don't want to give personal informations and another desnecessary informations, but no problem in creating a password, username and giving email. That is the safety protocol to play on any casino online.
There are a lot of good casinos where isn't hard to sign up, like Crypto-games.net, PrimeDice...