I think maybe it would be Profitable, if you never spend money on gambling, but you always play with the free money, so that when it wins it will be profitable and when defeat it's no problem.
So you mean we have to play always with no deposit bonus promos and some risk free offers, but it is really hard to find these regularly even that is good idea to play risk free there, that is good way to make profit when we have nothing lose there.
Why do you think that you're not wasting money by playing with those free money? Because if you're playing with those small amount means you need to spend a lot of time to reach the withdrawal limit and that time is nothing but money. If you spend that time for some other purpose, then you can earn money, so time is nothing but money.