As for the resonances, or as some call it "washy" sound in the Genelecs, I think it's mostly to people not being used to a full clean 50° radiation pattern. Most speaker radiation patters cancel out the mids vertically or horizontally, producing a more focussed sound.
The full linear in room response of most coaxials of course produces more reverb and for some people, this may sound too live at first since there are for more ceiling reflections, depending on listening position floor too. But this is the only issue. Other than that, clean radiating coaxials like Genelec, KEF, Kali and MoFI give you the nicest sweet spot ever.
Another hunch of mine for the Genelec 8361 resonances is the large baffle. Large baffles and tweeters/mid woofers don't work well together. The Genelecs have a kind of wave guide there and the mid woofer further acts as a wave guide, but maybe something of that "leaks" out. Note that the Genelc 8361 was a "post series" product that got added later. So maybe it's just as Amir said and Genelec "just scaled the 8351" up to make the 8361. But note that looking at the data, this speaker is still SOTA.
As for the subwoofer debate: my "old" Nuvero 170 have free field response of 23 Hz at -3dB. In room I measured about 10 Hz with that - I still have the measurement files. Still, after upgrading my system to KEF Reference + Subwoofers the bass is something else. The overall sound is cleaner, even more so for actual LFE effects and the speakers aren't pushed that hard anymore. Plus, subwoofers are very adjustable. Some rooms/speakers work better with 40 Hz crossover while some need 80 Hz. It gives you far more flexibility. Though note that good subs also come with a price. I tried the KEF Kube 12 in a dual setup in the beginning. The issue was these have awful impulse response and you even heard a sound like a bicycle tyre exhausting air for a short amount of time. This was unacceptable, even if all other metrics were good. And they were super prone to grounding loops. I bit the sour apple and bought the KC92, thinking I will by happy ever after with that money spend. And I was right, these are great. No more ground loops, no more resonances, stellar impulse response. Long story short, even for super high end ultra speakers, get a matching subwoofer. No speaker out there is really designed for LFE effects.