I don't argue that non line array systems can (given specialised design), give even coverage front to back and side to side, but this will require a specialist install and multiple differing "box" elements, most line arrays are travelling as 1 bass box 1 top box (given that they often have two dispersion widths) and a number of infills.
At a time when there are (in my personal veiw) maybe not so many "great" engineers about, the reality is that the average standard of concert sound these days is significantly better than it was 10-20 years ago and this is all down to the improvement in kit, particularly speakers.
I don't know what you by "specialized design".
All it takes is to aim the center axis of the loudspeaker at the furthest listener and figure out the angle it takes to cover the front row.
No big deal.
As far as the horizontal-what is different about the line array? At least decent point source speakers have large horns to keep the pattern where it belongs. Line arrays just "spray" it around.
I would not call a line array "1 top" unless you like that top to have a different coverage pattern at different freq (Which one do you choose for "coverage"?), and also has all sorts of spurious lobes shooting out the top/bottom and back of the array and within the "coverage area".
The ACTUAL coverage of a line array is quite different than what the marketing departments would like people to believe.
I would not disagree that large scale sound is better than it was years ago-but a lot of this has nothing to do with being a "line array".
About the time line arrays came on the scene-measurement systems became much less expensive-more available-easier to use and so forth.
Also the internet was coming around. This has allowed the free exchange of ideas-forums such as this-data easier to view/share which I believe has much more impact on the overall knowledge of what is really happening in regards to how loudspeakers behave (not as many believe) and acoustics in rooms.
So as a result there has been a lot more real engineering that has gone into loudspeakers than in years past in which there was a lot of "piling drivers into cabinets" without regard to interactions, cancellations etc.
And the overall quality of quality loudspeaker drivers is another contributing factor-again advanced by measurement and sharing of knowledge.
I believe the line array fad has just been riding the coat tails of these advancements.
I suspect by the end of this decade the industry will see less and less line arrays and more speakers that simply behave better.
These are my opinions and I am sure others will disagree.