The expression has been used so many times that it’s now a cliche. And ultimately, it leads to a problem. Organized religions—whether they be Christianity, Judaism, or Islam—provide people with rules and regulations. You can bemoan these all you like. You can talk about how stringent they are, how unfair they are, etc. But you’ll always come back to the same fact.
Societies are based on rules. When people lack rules, the result is chaos.
“Spiritual” can be used to describe anything. Taking heroin can be spiritual. Having sex with your neighbor’s wife can be spiritual. Any experience that produces momentary pleasure has an element of spirituality to it. So that term doesn’t work in the long term. Moreover, it can be used to justify destructive behavior.

Organized religions have existed for thousands of years and that’s no accident. The essentials to a healthy life—preservation of the family, faith in God, an adherence to good deeds—are provided in organized religion. When these goals are removed, we see a breakdown in society. A new set of rules are formed, and they’re usually more chaotic than the ones they replaced.
To quote C.K Chesterton: “Don’t take a fence down until you know why it was put up.”