Single way or multiway

and he will be right. Playing with a singular driver that may beam too early, ring at its breakup mode frequency is madness to me, but I guess companies must find their gimmicks.

but one doesn't need an overly complex crossover system to get class leading presentation of sound

Who is right, and who is wrong?

I disagree with your leading premise that there is a “right vs wrong”.

Perhaps if a single driver can do the speed of treble down to bass that can move enough air would be ideal, but doesn’t exist.  Therefore tradeoffs are inevitable- there is no perfect speaker design.

Also, there’s “higher efficiency” that’s seems to be ignored when comparing Guader offerings to high efficiency Voxative and Zu, the latter which can run on very low powered amplifiers down to SET tubes Sonics.

I’m a fan of Gauder’s products indicating excellent engineering, but I do not reach farther in declaring them “the” global spokesman for what is best/right/wrong.  

The issue with single driver speakers is covering  the entire freq spectrum humans are capable of hearing. I've owned Omega and Jordan single drivers, both were unsatisfactory in this regard. I suppose one could add subs and super tweeters, but I'd expect major problems with integrating them, and you've lost the principle of simplicity. 

There’s no free lunch with speakers.  There are many choices to be made, and every one of them has advantages and disadvantages.  It’s up to the designer to define the objectives and find the best path forward to meet it, but there will always be compromises.  Most companies only market the advantages, and don't bother to mention the downside of their offering.  A talented designer will try to maximize the benefits and minimize the impact of the cons.  

I had a pair of Omega and while they did sound very good they struggled with certain genres of music .   

After about a year I realized what I was missing, the sparkle and air of a dedicated tweeter.  Midrange was their magic, vocals and imaging really were their strengths 

I bought a really nice sealed acoustic 3 way and never looked back.