"Take home" challenges are excellent - they give an opportunity to create a common platform for discussion that every party feels comfortable with.
As for time investment, it's worth to dedicate 4-6 hours of your life to make sure the next few years of your employment are good for both parties.
It is not whiteboard that is a problem, but pressure of being evaluated by a random dude. It's like dancing naked. Whiteboard is a complimentary tool that should be used for visualization and demonstration, that's it!
Also, it takes years of experience and a great emotional intelligence in order to be able to conclude anything not obvious about a person after 1 - 1.5 hours of f2f communication. Let's face it - most of us are not there.
The best way is to simulate a real-case dynamics of whatever the job requires, for as long as possible, and give both parties chance to behave in a natural way.
All sounds great when you interview for 1 position at a time, but how does this scale if I interview for 4-5 companies in my job search? Considering every take home probably also has a full day interview afterwards, that's a lot of time investment.
As a company looking for people, do you want to have your 6 hour take home project to happen after the candidate has an offer? As a candidate, are you really going to spend another 6 hours, if you have an offer in hand?
It's your choice to interview for 4-5 positions, moreover, you will have those interviews whatsoever, so it can't be an argument :)
Most chances you are applying for a high paying job and do that once in 2-3 years on average, aren't you ready to invest a week of intense effort for that?
If not, you could choose to apply to a FAANG and spend 2-3 weeks studying craking the code interview-style books.
How much time do you think is reasonable to invest for candidate and a company to make a decision?
As a company I don't see a point in giving home excercise after an offer, but why are you asking? I will spend 12 hoirs if I consider a company better than one that offerer.
As for time investment, it's worth to dedicate 4-6 hours of your life to make sure the next few years of your employment are good for both parties.
It is not whiteboard that is a problem, but pressure of being evaluated by a random dude. It's like dancing naked. Whiteboard is a complimentary tool that should be used for visualization and demonstration, that's it!
Also, it takes years of experience and a great emotional intelligence in order to be able to conclude anything not obvious about a person after 1 - 1.5 hours of f2f communication. Let's face it - most of us are not there.
The best way is to simulate a real-case dynamics of whatever the job requires, for as long as possible, and give both parties chance to behave in a natural way.