Bingo. When presented with a buffet, people (myself included) usually have a fear of "missing out" the good stuff, so they just load a little bit of everything to their plate. At a buffet, you usually don't have the information about (1) how filling an individual ingredient is and (2) how well they go together. So each and every time, you end up with too much food which doesn't really combine. In the end, you leave too full and slightly unsatisfied. On a menu, the individual menus or plates have been tested for months against the cooks and guests, and the kitchen has adjusted plates which were always returned with leftovers to be smaller and/or removed meals that led to too much complaints
So basically, on a buffet you will get an untested meal designed by someone usually not competent enough to design it (you), every time.
Which I sometimes do. At which point people will look at you funny.
But you can't in many places and unless everyone does the same (unlikely) you end up getting your food when everyone else is about done.
I'm generally not a fan of buffets.
Common problem for beginners, but with experience you can avoid it using more advanced buffet technique and strategy.
One trick is to switch to a two-pass algorithm. Before you grab a plate, walk around the buffet area and look over people's shoulders, survey what's available, and make a mental note of which items you want most, which go together, and which will fit on your plate. Then grab a plate, get in line, and fill your plate without being blind to what's ahead of you.
You may mildly annoy the people whose shoulders you look over and your dining companions who have to wait on your slow process before they can begin eating, but it's a small price to pay for taking a buffet seriously.
Another trick is to look at what's on other people's plates, both people sitting at tables and people exiting the buffet line. You may notice a food on someone's plate that you didn't see on the buffet line. Maybe it wasn't easy to spot or maybe there was some other serving area (a dessert table off in a different corner) that you didn't notice.