Accuracy is the main plot.
The stories just the method of showing what an ER can do - even so they're so well written.
It's is not a show about big flashy attention grabby stories (Almost all the negative reviews) it's about showing the range of things an ER can experience from the boring and mundane to the absolutely chaotic and unpredictable. So yes it takes liberties but within the reals of reality - it is an ER don't forget people in real life depend upon it and also go when they don't actually need it.
Don't watch it if you enjoy fantasy story lines with questionable real-world treatments and procedures - watch it to see how something even boring and common is done but correctly and accurately.
Not an expert myself, nor do I work in Med - but damn unlike anything else.