Having displayed an interest in things mechanical at a very young age, my step-parents gave me the smallest Erector set when I was about seven or eight. It was a big hit, so a couple of years later they gave me the next size larger. In terms of enjoyment and entertainment, those were probably the best gifts I've received in 70 years.
Lately, I've tried to obtain a complete ferris wheel or merry-go-round-sized set (#12?) via eBay. I've bought some sets, but they were missing many parts. One thing I've noticed about them is that some kids seemed to entertain themselves by bending parts until they metal-fatigued and broke.
I've concluded that some kids "have it" and others don't. Those with imaginations and patience are able to build things. Those who are lacking both get their kicks by destroying and scattering the parts.
Recently, while "Googling" for "spur gear differential" I came across the most complex Meccano construction I've ever seen: a functional automotive transmission model, complete with planetary gears, spur gear differential, etc, etc.
Orrin