Won't claim this has never been true, but if it were true today, it'd be measurable and repeatable. Too many 3rd-party shootouts have proven this false, even after accounting for YouTube compression.
However, when we perform double-blind listening tests, 100% of us can reliably call out two particular competitors; one because of its squirrels and other artifacts, and the other because it never sounds anything like the real amp—multiple EQ (and perhaps multi-band compression?) stages seem to be baked in in order to, I dunno—approximate what they believe their customers think the amp should sound like? It doesn't sound objectively bad per sé (especially if you love gacked-out producers going ham on a djent mix), but it sucks that you can't dial it out.
Cliff knows who I'm talking about; he's alluded to something similar.
Yeah, I think some of these naysayers must only go to dad-friendly metal shows, where yes, Fractal is very common. Kemper still appears to be king in mainland Europe, and QC is appearing in more places, but Helix/HX is everywhere. It was all over Lollapalooza, which is decidedly non-friendly to dad-friendly metal, although Deftones played, who happened to be on Helix.
One particular company has seeded (given away) hundreds of their modeler to artists and influencers in the hopes of gaining traction. Not sure what the user contract said, but I'm guessing we'll see a bunch of those hundreds show up on Reverb once the no-resell date is up.
And this is purely anecdotal, but 5 of my top 10 favorite bands in the world are on Helix/HX (and I've heard rumors a 6th just switched over, but they're not touring this year).