They're basically an EPL all-star team. You can't be too hard on them because they are such a small country, but given their talent level you can say they've underachieved the last few years. A totally mediocre US team very easily could have beaten them in 2014 in the first knockout game.
They've had a couple of "golden ages" where they happen to have a group of great players peaking all at the game time - one in the 80s to early 90s and a current one that started in about 2010 - but very little success outside of those periods. They were even #1 in the world at one point in 2015.
They might have more raw athletic talent than any other team in the tournament, including Germany or Brazil, and have elite talent at every position. There isn't a single position group you look at and say "yeah, they're kinda vulnerable there."