Jesus healed ten lepers. Only one came back to thank him.
All ten got the healing. But only one "got" it. Only one was awake to the blessed reality of what happened.
Gospel wakefulness is rare among Christians. And, yes, I think you can be a Christian and not experience gospel wakefulness, although it is dangerous. You've got the healing; you just don't walk in thankfulness, but in . . . something else. (And Jesus covers that too; I don't mean to imply he doesn't or that some emotional reaction is contingent for salvation.)
The older brother was not not a son, after all.
But if you are a Christian who has not experienced gospel wakefulness, you will always struggle more deeply with religion as a cover for your sin. Your worship will be less free. It will always be a bit more like Cain's offering than Abel's: the fruit of your labors (acceptable as grain offerings but not faith-full).
The "problem" is that you can't make yourself awake to the awe of the glory of the gospel. God has to do it for you. But it would be wise to work out your salvation with fear and trembling. Press in and don't stop until you've gotten to the "wow" moment.
Recipe for Gospel Wakefulness
What Gospel Wakefulness Does to a Church
Why Gospel Wakefulness is So Important