A bit late to the party but I'll give my 2 cents regarding amp modeling quality.
It's true that since a few years you can get excellent tones even out of very cheap modelers, but good tone doesn't necessarily equate to good modeling.
E.g. Gilmour recently revealed that, back in 1994, he recorded the solo for Coming Back To Life that ended up on the album with a Zoom rack unit (and still continues to use it today to record demos), that's always been considered a pretty good guitar tone by his fans, but I bet most of us who have used one would agree that Zoom devices from that era probably represent the shittiest amp modelers ever made.
This basically means that if you have the skills you can make shitty modelers sound great... Or, on the opposite side, make great modelers sound shitty.
And this in turn means that the subjective quality of tones one could get out of a device isn't a measure for amp modeling quality... The only measure for that is accuracy, a word that probably some of you don't like or don't care about, but it's really the only way to tell if an emulation is objectively good or not.
And if we talk strictly about accuracy, I'm pretty sure Fractal still has a pretty big advantage over most competitors.
Before going digital, for several years I mainly used a Hiwatt head as my main amp and Fractal has been for a long time the only modeler that really nailed that amp among the ones I've tried, even 11 years ago when I got my first Axe FX II. From that point in time it only got better in replicating some of its nuances.
The Helix (not Stadium) model sounds nothing like the real deal, it has a "nasal" voicing and totally lacks the harmonic richness of the real Hiwatt, let alone the way it reacts to drive pedals... The real one (and the Fractal model too) when you find the sweet spot on the level hitting the power amp, makes even the dirtiest and fuzziest distortion pedal sound smooth and creamy, good luck replicating that behaviour with the Helix.
It was one of the oldest model in the Helix though and I hope they significantly improved it in the Stadium (I'll definitely try it when I get a chance).
Over the years I've also tried Kemper, Headrush, Eleven Rack, Mooer, Nux, several plugins and some other modelers I don't even recall atm, none of them could nail that amp either.
Till now the only things that come close are some NAM and Tonex captures, but having to deal with captures is still a drawback for me.
I could say the same thing about some drive models and effects, good luck finding e.g. an Electric Mistress model in another hardware modeler that really sounds like the real one, or a univibe, a big muff, a tube driver, a bb preamp, a dist+, a colorsound powerboost... and so on.
(The Fuzz Face and Big Muff models in the new UAD plugin really surprised me though!)
In short, I don't think at all that modeling (generally speaking) has plateaud and there can still be significant differences between different devices/brands.
How much that matters to each individual user is a different matter and, being a subjective opinion, isn't really up for debate.
