I think I posted in here in the past, but I just wanna say one more thing.
The main reason why modern bodybuilders don't do full body training is because they are deluded into believing the bullshit that TikTok steroid junkies teach them. And according to these TikTok steroid junkies, doing a ton of isolation exercises spread out to six days per week is more alpha and more backed by bro-science. When in reality, the legends of the past like Bill Pearl, Steeve Reeves, and Reg Park did full body training and built their bodies effectively with them.
Nowadays, idiots who watch YouTube see CT Fletcher curling and shoulder raising and they all conclude that that's how real men train.
IMO
The part about the effect of poor advice from social media is valid but pertains for the most parts for the ones you refer to as idiots. There are some idiots for sure but I'll give them a little bit of the benefit of the doubt and say they are mostly uneducated or uninformed.
The rest is off target .
The Title and the OP refer to bodybuilding but the thread predictably got to wandering into some of the fitness, strength, cardio and sport specific stuff. Let's get back to bodybuilding specifically for a minute. Hardcore, goal driven, single focus bodybuilding.
The main goal of bodybuilding training, at least for most of the year, is to
build the body meaning to build bigger muscles, it's right in the name.
With rare exceptions over the course of your training life the goal of lifting is going to be getting each muscle as big as possible.
I can't think of a reason why anyone would want to take longer than necessary to do this.
The fastest way to do this is to go through a little cycle where you hit each bodypart with the highest level of intensity possible and then recover and do it again. Over and over as many times as possible in any given time period.
Each muscle has a different speed of recovery. Let's say your Chest takes 5-6 days and your Triceps take 2-3. IME those are pretty good numbers for the majority of people.
How are you going to work that into a full body routine and satisfy both of the mandates- highest level of intensity and as many train & recover cycles as possible? You are not.
Another problem preventing the best possible progress in a full body program is with getting the highest intensity possible itself. Although you may be giving it all you got all the way through your workout the actually forces being generated drop off and continue to decline through the workout right after you finish the the first true balls out set. The intensity drops off to an unsatisfactory level pretty quickly. The bodyparts trained in the last half or so of the workout are under-stressed, at some point too far off the level needed for maximum hypertrophy.
There is no reasonable way around that, you can't recover all your resources 100% during the session unless you were to make it stupidly long.
An intelligent split solves all those issues, You can train each muscle as soon as it's recovered and you can ensure that each muscle gets a very good dose of training at when fresh at the start of a workout when intensity is at or near it's highest level. Most people have a life to live so most programs are still not perfect but much, much better than full body.
A serious bodybuilder would want every last tiny percentage out of their program. Not a good workout, or effective or enough. Not speed or power or cardio. All that shit is secondary and maybe a bonus. Just want 100% of the possible hypertrophy.
I want the muscle I would need to win the O. I don't give a shit about any athletic ability, how much I can lift or my VO2 max. Many of the responses in this thread are just fine for those who lift for reasons other than these specific goals but that would require asking a different question.
PS - I love those old times guys and respect them as much as anybody but their are now tons (millions?) of guys bigger than a Steve Reeves and all of them would get dwarfed by any modern pro. And with possibly a few exceptions like maybe Reeves they didn't train exclusively full body.