Simple physics details the problems with horizontal speaker alignments and the acoustic issues that occur due to having multiple drivers interfering with each other.
This is not to say they cannot sound good, however, the nulls/cancellations
WILL BE PRESENT. This is unavoidable. So straight ahead,
on-axis, it can be great. What happens when you are 1', 2', more... off axis?
6" and 8" Woofers take up space and need a a bigger cabinet. Add to that a mid and a tweet and you've got a lot of real estate taken up. Still no guarantee about PH and Sensitivity.
No, the fundamental change is the paradigm shift in furniture and room design that needs to take place. No more built-ins, entertainment centers, cubbys...
None of it!
Of course, this leaves the possibility of concentric or coaxial drivers as a possibility, but these too have their own set of issues. Probably the most common that I've seen is poor FR throughout the range of the Speaker. This isn';t to say that there are none that perform well, but the better ones are far more expensive than most want, and they will not necessarily be a good match with your mains.
So back to compromises we go.