When listening to music from a two channel source, it's natural sound is two channels, no more.
These newer receivers offer various methods of taking those original two channels, applying various algorithms, and "fake" additional channels out of basically thin air.
Obviously, the nature of the overall sound will be changed. For better worse, it does satisfy the need some feel that they must use all the channels they paid for all the time. Heaven knows, modern receivers offer many. many variations on this theme from which to choose.
Whether one likes the end result is up to ones personal tastes.
Personally, I, and some others here, prefer my two channel music straight up, with just a touch of subwoofer added.
Feeding a sub is another story and generally not too big a deal. All they generally do is combine the common bass into the LFE channel and can be implemented quite successfully with a two channel source without mangling the original two channels with many receivers.
As for using all the channels you paid for, you don't always use all the horsepower your car is capable all the time. If you ran it flat out all the time you might run into problems. As long as it's there when you need it should be your goal.