Mid-side processing can be a powerful tool when mixing, but if you don’t know what you’re doing, you can also screw it up, badly. I totally agree with this point:
In truth, 90% of a great mix comes from a really solid foundation in basic engineering and really strong decision making.
However, you can use mid-side to add a little something to the mix.
There is no substitute for getting it right in the recording. The modern era’s tendency to Fix It In the Mix creates tracks with suffocating dynamics and no heart.