>>9947152China has had Transformers since the 90's. There's a reason the 3P scene blew up over there.
The real answer is generations got way more complex than most of the past kids lines, and kids prefer more streamlined and simple transformations(and more importantly, their parents). There's always pushback when a line gets too complex. by having these simple lines it helps Hasbro curb this so they have a product for different consumers.
And while retail kids lines are probably too simple, Modern generations are way more complex usually than the G1 and BW toys they're homaging. Its amusing to me to see people who grew up with flipchangers and transformers with 4 steps tops complain about modern simple lines.
Transformers in general has a bigger audience world wide than it did before the movies, so there's more kids buying them in general, and not all of them are good at following long instructions. Transformers used to be a "brainy kid" toy, they were basically puzzles so they attracted kids who wanted a brain teaser.