Diversity of opinion over what

Yes, I think that Jmcgrogan2 nailed it. I personally do not use the word synergy (it's a bad word in my vocubulary) but use 'impedance matching' instead but the undelying principal is the same. Electrically the amplifier must be able to drive the speaker it's being connected. And, if the speaker is too capacitative (for example) then the amp must be stable & not break out into oscillations (which is often manifested as harsh/brittle sound), if the speaker is a low impedance load in the bass area then the amp must have sufficient current delivery.
Like Jmcgrogan2 wrote the speaker cables & pre-power cables also make some difference in the sonics.
It's entirely possible that the amp-speaker interface was just fine your case but it could have been the cables or some electronics upstream? Debugging this is a hard & time consuming job but if you do go down the debugging path you end up learning a lot about what makes your rig tick & that is always worth the effort. The easiest thing to do is to dump the amp....
Anyway, the amp-speaker interface has to be considered very seriously esp. for 99% of the speakers in the market that continue to be ill-designed.

As Bombaywalla says no component is ever heard in isolation; we are always listening to SYSTEMS. I am convinced that there is just about nothing that cannot be made to sound bad by incorrect choices elsewhere in the system. I bought my Apogee Duettas even though they sounded horrible in the store; they are great speakers when set up properly. I agree about the JM Labs; I had a pair of Mini Utopias which could not be faulted for accuracy of sound reproduction but which I was not comfortable with; many others would be. Part of the time I was using my MF NuVista M3 but I had the same impression on other amps as well.

I also remember the prior JM labs as being analytical and fairly bright, even for my taste. I think that is possibly the cause of the disparity of opinions in this case. I could not live with those speakers easily without a front end to tame them. The latest series of Focal Utopia speakers are a whole different story. Superb speakers .... amongst the very best of all the ones I have heard in recent years.

How we hear if different for everybody, especially related to culture and language. Many years ago an article appeared in FI magazine that explored how people in the UK and the USA had different 'hearing'. Part of that exploration was aimed at the often used term 'british sound'. Still true, so it is no wonder that we have a diversity of opinion on what speaker sounds 'better'. Recently this difference of hearing is being explored with Asian people.

Years ago, I asked the reviewers from a couple of the mags to publish full audiological reports. I swear a couple of those guys had high frequency loss. I used to have one done every few years. Now I'm old and don't need a test to know I can't hear. That and mi esposa and grown kids tell me so, loudly.