I'd make one change to the advice - instead of "Buy a rower", I'd say, "Buy whatever machine you will actually use." Whether that is a rower or anything else, the point is to do something, and do it consistently.
And, protip: If there are clothes hanging on it, you've failed.
Anyone can attempt Dwayne Johnson's workout and diet, it's published all over the place. The reason we aren't swamped with ridiculously swole people isn't because it's a secret, it's because it take extreme dedication (and moderately good genetics, but nothing special).
And if you're all about optimization and time, you could get a VersaClimber cross crawl club model and spend 8 minutes (2 mins warm up, 4 mins HIIT, 2 mins cooldown) for better (clinically proven more effective at causing a metabolic shift) results.
Why doesn't everyone do this? For one, the intensity makes people ill when not used to it. That's why it's not in many clubs. For another, unlike rowers or cycles, you can't just sit on your butt or coast.
(In addition to road cycles, I own water rower, versa climber, and hydrow. The VersaClimber kicks your ass.)
Are you able to actually look forward to an "ass-kicking" workout on daily basis ?
If someone did bring up setting a fitness challenge, I'd say buy a rower over treadmill or bike. Rowing does add more of a full body workout over bike.