Some good points but "of the world" is referring to sinful matters which take precedence over our walking with the Lord.
Is it "of the world" to go shopping? Is it "of the world" to exercise, whether that take the form of going for a job, lifting weights, playing a sport? Is it "of the world" to hunt or fish for food? Is it "of the world" to tend a garden?
There are many activities we can be involved in outside the church which may be in the world, even as we are, but no "of the world" in the sense of being sin.
As with most things, any of these could be participated of in a sinful manner, but they can and are participated of in non-sinful manner also.
Jesus and His disciples and apostles took time to fish, walk, eat, attend weddings, celebrations, etc.
We have to also remember that everyone born again of Christ is saved, is a brother/sister in Christ, and are at different stages of their spiritual lives, which can include being a spiritual baby or spiritually mature or any point in between. Each is saved, each is no longer "of the world" yet each persons actions and lives won't match one another exactly. We all partake of things in this world, some wrongly, some rightly, oftentimes a mix of the two. Even so, the weakest, most immature born again person is just as saved as the strongest, most mature born again person.