Withing the controlled dispersion, response should be even. In an anechoic chamber, it's still bad in my opinion if shifting my head a foot up or down changes the balance of treble and mid-range when a coincident coaxial driver would solve that problem.
I don't think there is one right way to make a speaker. Every approach introduces compromises. I haven't heard a single speaker design element that is a must have for better sound.
I have heard well reviewed speakers with:
Coaxial drivers (KEF) time aligned drivers with the Vandersteen and Thiels,
speakers with and without waveguides,
horn loaded, phase plugs, bipolar electrostats and quasi-ribbons,
ported, sealed, side drivers,
active subwoofers, active speakers, active bi amped speakers, passsive bi amped speakers, bi wired speakers,
10 inch bass and mid drivers, 4 inch bass and mid drivers, 6 and 8 inch bass and mid drivers, single full range speaker drivers
silk tweeters, ring radiator tweeters, folded ribbon tweeters, ferro-fluid tweeters, berrilium tweeters, silk tweeters,
Aluminium, paper, silk, berilium, diamond drivers,
didn't make one better than the other simply due to the presence of these elements in the design phase. None of these would I consider necessary to sound better than another.
You have to take both two speakers and actually listen to it to see if it's what you want imo. The design decisions used to get the sound you like are usually optimized for that specific speaker to tackle its specific challenges.