In demand DevOps candidate here. I had multiple six figure offers from companies, and still picked the job that required a 4-6 hour project I completed over 2 weeks in the evenings (that I was paid for).

Provide the right work environment and perks, and people will "jump through hoops" if they think its worth it.

I don't know, if a company asks me to complete a simple test application, I might be more inclined to talk with them, because it means my interview (ostensibly) would be about the code I'd submitted. Which in turn is much more like what a day in the life of a developer would be like at their company (I write code, review with team lead, repeat, or somesuch).

I think really good candidates will enjoy working on relevant issues and not working on silly interview questions. If anything these "hoops" seem like exactly the filter you'd want. You want people who enjoy jumping through those hoops every day after all.

The key is to give this in liu of a 6 hour panel of interviews. So your project should be 4hrs max. And don't add in vague time waster 'bonus points' for doing more details.