I think that both types of IRA's are vitally important and serve a purpose along the path to financial independence and are essential to the laddering process. The question is not which, but rather when to use each one.
As it relates churning credit cards for travel, those in the "FI community" that are highly focused on directing every available resource to procuring their freedom at the first available opportunity during the wealth building stage will find travel hacking to be used far less frequently than those already financially independent.
It is unrealistic to think you will incur no travel expenses doing this. Even an 80% cost savings still requires 20% capital to be directed to something that may not need to be during this stage. There is also pressure to use all the points before they expire, redeem in a certain period affecting expenses on other parts of the trip, have account activity within a certain period, keep cars a day longer to get the full benefit, limitations on what may be combined per trip adding further expense, shortages that result in mileage purchases...all resulting in capital being diverted from potential savings and investments.
This is not a conversation about the value of it, but again at what stage along the journey it may be appropriate. During the wealth building stage, trips to Perth are less important than savings on groceries and gas in my opinion. I have over 6 weeks of paid vacation per year and use every single day with most expenses fully covered as my vacations are domestic in nature. There should be plenty of time to go to Perth and Frankfurt in a few years...
In the final analysis, a failure to travel hack is not a mistake for those in the wealth building stage with other, let's call them "priorities" at the moment. Also, most certainly if you have debt then your role in this conversation should be self-evident...