Half the fun I had playing with Lego when I was young was unfolding plots between the minifigs - you'd build something, then have your minifigs interact with it. I'm not really familiar with Meccano, but as I understand it there's no 'human' in it with which you can project yourself. Meccano can let you build cool items, but Lego can let you build cool items, an environment to put them in, and people to interact with both of those things. Lego seems more versatile in satisfying a flexible imagination.

Also, suggesting that the decline in quality of modern engineers is Lego's fault is an interesting variant on the usual 'kids these days' crotchety-old-man talk.