Not sure what is meant by that commenter, but weight loss and strength gains are common goals which running isn't the most efficient at achieving. Obviously, it still impacts these and, obviously, those aren't goals for everyone.

Running is great at improving cardiovascular output (honestly not sure how it compares to biking and swimming), but that isn't all of fitness.

According to this [1], running is much more efficient at improving cardiovascular endurance than biking, in terms of time spent training for a particular gain. Particularly trail running.

[1] https://www.amazon.com/Training-New-Alpinism-Climber-Athlete...

(ps. As someone who is sort of a weekend outdoors entusiast, without being any kind of a competitive climber or particularly interested in training, I thought it was an interesting read and would recommend.

It's a solid book, although I don't recall the bit that you're citing. I didn't read it that thoroughly. Started it and realized that I'd rather work towards 5.13 than the summit of Everest/Denali/whatever.

Body weight exercises such as pull-ups, sit-ups, and push-ups are the best for fitness.

Again, this depends on how you define both "best" and "fitness". What's best depends a lot on what someone enjoys. I would rather do an activity I enjoy for 40 minutes than get the same benefit doing something I hate for 20. Likewise, fitness means different things to different people and at different times. You may be focusing on cardio-vascular fitness, or on strength, or speed, or weight loss, or performance in a particular sport...

Or, you know, "do something". Throwing a bunch of complexity and equipment cost at someone who doesn't currently exercise at all isn't likely to help anything much. Pushups and situps require only a clear stretch of floor.

Sure! If you're just getting started and can stick with that, maybe that's best for you! Just not for everyone.

I think calisthenics are great, but they focus more on muscular strength than cardiovascular.

There are only so many push-ups you can do before your muscles are fatigued. Running, swimming, and cycling are better for cardio because you can do them for great lengths of time.