Obviously, anyone who wants to bodybuild competitively is going to have to be proportionate (according to day's standards), so it would make zero sense for an aspiring bodybuilder to half-ass (or skip) leg training.
On the other hand, most of the guys we see in gyms aren't competitive bodybuilders, nor do they have the desire to be. Today, the goals people set through weight training are more diverse than ever...and many have zero ambition to build a physique according to modern bodybuilding standards/proportions.
Personally, I prefer the proportions of the 70's and 80's over those of today...by a long shot, yet those proportions (which were considered the competitive ideal at that point in time) would attract harsh criticism in today's line-up.
Today, there are a lot of non-competitive "bodybuilders" (i.e. people who use weights to build muscle in ways that appeal to them/ are in line with their personal goals, and I don't think this is something we should criticize. Yes, I personally think it looks odd to see someone with extreme upper-body development and zero leg development (that doesn't happen to often), but keep in mind that what might be considered ""ideal" proportions will vary according to the individual.
For example, Big Ramy had proportions which were good enough to earn him 3rd place in the toughest bodybuilding show on the planet, yet the average person will look at his upper-legs (relative to his calves and even in comparison to his upper-body) and think his proportions are horribly distorted. Even according to bodybuilding standards in the 70's and 80's, his lower body would be considered horribly unbalanced, yet he placed 3rd in the world in 2017.
Today, Arnold and Haney would be considered disproportionate (their legs in particular), yet in their day they were considered the best proportioned (or among the best proportioned) competitors in all of bodybuilding.
Competitive bodybuilding aside, many guys have completely different goals altogether, so we can't really penalize them if they don't care about building big legs...or if their legs are under-developed according to bodybuilding standards. Today my primary ambition is armwrestling, which requires me to train many upper-body muscle hard, but not legs...and I am OK with that. To each their own.