Not quite.
Front to rear mixing isn't too bad.

Using differing speakers left to right can sound "ok." It will only sound as good as the Speaker with the least quality.
Yes, you could process different speakers and get a decent sounding system BUT , the materials used to make the speakers all have their own unique sonic character that even great measuring equipment sometimes can't measure but our ears pick it up easily.

The difference between the way paper cones and say a poly or carbon or metal cone sounds is relatively easy for humans to hear though the eq curve could read perfect.

The most obvious expample is metal vs silk tweeters.

It's a night and day difference no matter what the rta says. You just simply cannot make certian materials sound like others.