I think what you're saying in your second comment is "don't get stuck on following a routine exactly. Figure out what works for you and do that; it doesn't have to be exact." And I agree for people who are already familiar with a variety of fitness routines and their goals. But the problem with that statement for novices is they have no idea where to start. Do I do 50 push-ups a day to get a huge chest? 100? Run 5 miles? Both? Sit-ups? Bench seems scary and I don't want to be a bodybuilder or get a gym membership so maybe I'll do stuff at home. Then you end up like me, spinning your wheels with a shit diet and thinking your genes just weren't cut out to be fit.
Take the basics for each muscle group and expand on them.
New browsers to this sub don't have any idea what "basics for each muscle group" are. That's why routines are helpful where someone has already divided up the exercises for them.
If you see someone who clearly knows what they are doing then pay attention and try a couple of the exercises that they are doing
Dude, that's exactly what these posts are. "Hey, that guy went from skinny to super jacked. If I just copy exactly what he did, maybe I can get there too!"
you clearly did not do your research before you started
That's exactly the point. I did research online in dozens of places, but there is an absolutely insane mountain of information out there about fitness of all kinds. Yoga, karate, tae kwan do, BJJ, distance running, cycling, hiking, rock climbing, power lifting, body building, sprinting, track and field, gymnastics... you get the idea.
The reason behind including diet, a precise routine, height and weight, etc. in progress photos is to compile all of that information into a single repository readers can use, so they don't have to search on a thousand different websites for how to get to their goal body.
And yes, I made more progress in 4 months following a strict diet and muscle-building routine than dicking around at the gym, running a mile here and there, doing pushups, and other things that I thought would get me jacked. I don't know why that's surprising.