Tabata makes you want to vomit if you don't have at least a moderate level of fitness. Even if it's great conditioning. So here's the problem.

We go on about what's optimal from a raw time perspective, but time slows subjectively when you suffer. So people who don't conceptualize themselves as athletic, they may have insecurities if not outright skepticism, aren't going to last.

You can make a culty cultural glue to get habits to stick (because fitness is all about habits). You can do CrossFit, the social and positive aspects. That encouragement can bring habit and a change of self perception.

But if you're just a self-driven type, and you're dipping your toes in the water, my observations are that whatever is fun (an individual experience) is what you'll be creating a habit with, and time foes quickly. So explore a brunch of things until you encounter fun. Tennis, running club, weightlifting club. Etc.

So my point is that fitness is a problem around how people experience exercise and training, instead of what's optimal in a paper or in terms what's efficient in terms of time.

Was this prematurely dismissive? Maybe, I'm going by the comments.