The expansive menu may be one of the issues they have with getting the food out. Having many items certainly gives the consumer more choices, but it can also create a massive log-jam in the kitchen and bog down service when you get a 10 top and no one can make up their mind what they want. I'm a fan of "do 10 or 20 things you do very well and nothing more".
I always agree with that, unless you are a pizza or Mexican joint, where different menu offerings only require changing the shape or toppings of the food.
One of the biggest mistakes that restaurants make is trying to be everything to everyone. I've seen restaurants rescued by simply preserving 4 or 5 of their most popular items and eliminating everything else from the menu. Quality, margins, service, and identity all benefit.
Unfortunately too many are willing to succumb to the lure of variety (thinking they are going to capture additional market), but instead they dilute their brand, cut their profits, and impact their overall quality. Sure, they have folks that say "Wow, I love your new wolf-nipple fritter," and they use that to justify their decline in other ways.