That assumes a very straightforward calculation of being willing to 'pay' time to fufil various outcomes.

I am making an educated guess about a key factor of people's costs, and I am addressing that factor. Time is, in fact, very limited. After you subtract work and sleep and other necessities (bathroom activities, kitchen activities, meals) there is very little free time left in the day.

I am also writing from the point of view of someone who is not yet sure what the outcomes are. I touched on outcomes and I will touch on your claims about outcomes, but I deliberately am trying to write from the point of view of someone who does not know, because I don't want to set myself up as an authority, I merely want to reason with the reader on the basis of what the reader himself already knows or can work out for himself.

Personally, I'd find walking a lot more enjoyable

That's you. I am addressing myself to the writer of the essay who abandoned exercise (for the duration of their weight loss) and to anyone like them. Since they abandoned the exercise program, evidently they did not find it sufficiently enjoyable to do it. The exercise program was in all likelihood walking. Or, if weights were included, it was in all likelihood one of the more common, more time consuming resistance training programs.

The reality is that walking is not enjoyable to many people. Intense resistance training is, admittedly, even less enjoyable, but it can be fantastically brief.

and it would have clearer other benefits:

That's biased. Under what circumstances are the benefits clearer? If you want to be fair, you either take a position of ignorance with regard to both, or you take a position of knowledge with regard to both, in which case either their benefits are both clear, or they are both unclear. To treat the benefits of walking as known and the benefits of resistance training as unknown is slanted.

it certainly makes you good at walking without getting tired/sweaty, just like weightlifting makes you good at lifting weights.

This implies that resistance training only makes you good at resistance training, which is wildly false. After starting squats, I found my ability to walk was transformed. I really do not want to get into this, in part because it's TMI about myself. So I'll leave it at that.

Different people also find different routines easier. Some might find 12 minutes easy to find and fit in, but others would get into the swing of walking to work, whereas a 12 minute slot of intensive weights would not be enough to click as part of their routine.

I would be willing to bet that for most people, walking to work is not realistic, for a variety of reasons. In any case I am addressing myself to an audience who has abandoned exercise, and I am guessing that the exercise they abandoned is probably walking or something like it.