Gimmicks ruined the Transformers toyline. The first wave was excellent - small Autobot vehicles that transformed into robots: the 'real' Transformers. However, most fans don't know what on Earth Hasbro was thinking with the second wave. Cassettes? Transformers just don't transform into cassettes, as the now much quoted phrase "M1N1CaR NOT KaSETE!!!" sums up perfectly. These cassettes, considered by most fans to be worse than GoBots, also had a gimmick, the first of many lame and pointless gimmicks. Rather than being Autobots, as all previous Transformers had been, these tapes were called 'Decepticons,' a supposed *second* race of Transformers and enemies of the peace-loving Autobots. The 'Decepticon Tapes' also came with another gimmick: weapons - a blight upon everything the Transformers stood for.
Of course, most Transfans had long since stopped collecting by this point, but after this failure, Hasbro continued to try and keep the franchise alive with more gimmicks; planes, cassette recorders, guns and even larger cars, which were an obvious attempt to reclaim what fans originally liked about the series. The last hope for the line was a toy they called 'Optimus Prime,' which was basically like the much-loved Huffer, but bigger and with lots of gimmicks.
Naturally, Optimus Prime was a failure. Kids couldn't carry him to school in their pockets, and he came with lots of what is now known as 'kibble'; guns, a trailer, missiles etc.: lots of extra gimmicks that ignored the fact that what most fans of the 'real' Tranformers liked was the fact that the toys were self-contained and peaceful. With the addition of guns and an enemy to fight, Hasbro had sealed the fate of the Transformers line, which, after some further pitiful attempts to revive the line, would draw to a close in 1990 in the U.S. (The toys continued in Europe and Australasia, continents that still hoped to see a return to that one great month in 1984.)
Of course, as we all know, the U.S. line returned in 1993 with Transformers Generation 2, heralded with a gold vacuum-metallised Bumblebee. But that's a different story...
(I first posted this
twelve years ago now, but I feel like it needs an airing every so often. :p)