Thinking the dharma is a form means you're not practicing whenever you're not doing that form. It means enlightenment is still not here. Something to feel bad about, more division between samsara and nirvana. I know I'm really good at turning the Three Jewels into another guilt trip. We all know someone who could receive a literal wish-fulfilling jewel then say, "Gosh I don't deserve this."
I was actually thinking about a related question this morning... if nirvana is unconditioned, why does a conditioned practice matter at all? And related to this, how is one conditioned activity better than another? I think I read a Zen story that gets at the issue, where a student posed the same question to his teacher. The teacher paused a moment, then took off his sandal and slapped him across the face. "That's why!" As long as suffering exists, regardless of if it's a daydream or a funny mistake, then the work of a bodhisattva isn't done

Silly answers to deal with the silly things we do to ourselves.
Whether any activity is actually beneficial is individual. Working with our greatest defilements first, we notice that their branches reach many parts of our lives. Ideally, you try to cut defilements as close to the root as you can. That's the need for specific forms of practice. But if you're overrun with blackberries, you don't just cut the root and leave the dried up briars all over your garden. That's the need for post-meditation practice, by the fence, around the cucumbers, on the ski slopes...
Just be honest with yourself about hobbies. The danger isn't necessarily in having down time or from a puritanical viewpoint "wasting time", but in finding new things to make into the ol' Big Deal© and therefore forget our commitments. Our duty is to work tirelessly out of love for our countless mothers and children lost in suffering. I can think of no better way than marrying practice with everyday life, where these beings actually live!
And since you asked...

I enjoy taking walks, painting landscapes, playing piano, writing terrible poetry, working on my constructed language...

I'm also deep in the Song of Ice and Fire series by George R.R. Martin.
Please take the above post with a grain of salt.