You are close to something. You've found the division between worldview, and religion. A worldview is bigger, and is individualistic - but generally founded upon tenants shared by others. "a framework of ideas and beliefs forming a global description through which an individual, group or culture watches and interprets the world and interacts with it as a social reality."

I will say: There is no accepted definition of a religion. There are hotly debated definitions, but no concrete and agreed formation of what it constitutes.

However, generally speaking, a religion is a set of socio-cultural systems, generally tied to a set of beliefs, that tend to have supernatural or spiritual elements. However - the systems are essential, the beliefs are not. [0] Many agnostics and atheists follow religious practices, and form their own religions. There are Christians who do not believe in Christ.

Because the core of a religion is social and cultural, it greatly varies in time and place. The Christianity of Early Rome would be unrecognisable to most Christians today. The religion has changed almost every single practice, over time, because of the cultures that have influenced it today. [1]

[0] An example would be "Jewish Atheism". It is a religion, with practices and rites, but it does not carry with it supernatural or spiritual beliefs. Another would be "Mainline Protestant Buddhism", also known as Secular Buddhism.

[1] An example of one of the most important rites in early Christendom that is no longer regularly practiced in Rome, would be the washing of feet. The host welcomed their guests on their knees, caring for them. Society moved on, shoes and roads changed, it no longer became necessary, and the religion changed around it.