they are a much bigger car than any cossie so will always drive different. Most cossie drivers spend time and money making thier car as nimble and chuckable and aggressive as possible so of course something like an M5 will seem boring.
Theres no doubting the performance of an M5, high speed, good handling, good comfort and no drama. If thats what you want then fine. if not......
Its a 5 series, its a big massive saloon car!!!