i don't agree on them having problems in the first place, in respect to other adventures, Lucasarts' and others'.
I have not played many of them. why? same reason i don't play now many other retro games: they have a slower game mechanics than i expect them. it's the game fault? no. it's just that, in this case, i got first to Monkey Island games and their interface had taught me what to expect!
Now, years gone, Lucasart games from that period are slow too! so it's just a matter of personal expectations, concentration/dedication and time allotted to the present task.
if you just check them not withstanding the playing pasrt, those Sierra games were real gems! way more layered and elaborated than many other concurrents, like Monkey Island, that, on them, had in turn great audio and great fun.
Sierra games were hard, they still are with a solution in your hands, but no more than platforms or shoot 'em up like [insert name here]!
in my opinion it's not the game, and this is valid very often out of this context, that is particularly flawed but the reviews on magazines, the hype or the scorn to be fruitless and ininfluent.