Guitar playing from the guitar player's POV is not about AB tests though. If IEMs trip your trigger; have at it. If playing through a plastic turd of a powered wedge trips your trigger, have at it. If playing through a Triple Recto trips your trigger, have at it. You can "correct" someone all you like but if they are successful in their own self-set criteria; your correction is falling on deaf ears. Sometimes literally
I think one possibly relvant issue with FR systems (regardless whether it's IEMs, standard headphones, a wedge, studio monitors or whatever) is that you can't just easily try things out.
Hop into any more or less wellsorted music shop and you'll likely find quite some amps/cabs to fool around with. Usually you can even combine different amps and cabs. On the contrary, to check out any kind of DI stuff, they may have their "modeling corner" with a presentation thingy and a generic (cheap, so nobody steals them) set of headphones.
Number of IEMs you could try with? Zero (and they could easily have disposable earbuds).
Number of FR wedges you could try with? Depending on the shop's size perhaps quite some but you gotta head over to the live/PA department with whatever modeler. Let alone they will very unlikely have some of the rather guitaramp-modeling-targeted models there for comparison.
Number of studio monitors could try with? Quite the same thing.
Number of IRs/profiles you could check out in case the internal ones don't satisfy you? Zero. Even if you had a laptop with you with all required software pre-installed, I'd bet not one shop would allow you to connect it to their Helices, Kempers and what not. And we all know how much of a crucial thing IRs are (less on some, much more on other devices, for instance, I found my Amplifirebox to sound pretty meh out of the box, but with the right IRs it's still holding up today).
What I'm saying is that a) Modelers and FR monitoring to serve as the opposite of instant gratification, whereas b) amps/cabs are often made for just that. Add to this there's sooo much more variables inside a modeling signal chain, it's really tough to get things sorted. Defenitely not for the faint hearted, especially not in case you want to use this live (and even less so in case you don't go for IEMs but wedges). Otoh, traditional amps and cabs are tried and trusted (especially tried!) for live usage since decades already. With pretty little design changes, hence a rather manageable amount of options to choose from.
From my personal experience: Have I been happy with my first endeavours in the FR world? No way. I'm old enough for having owned several, partially gorgeous old-fashioned rigs and I have often enough been in situations to enjoy those setups in loud'n'proud environments.
Yet, not only that (pretty much all of a sudden) I had to use a silent stage option (theatres just started demanding them) quite some years ago already (so I had plenty of time to get used to things) - no, I also instantly realized what a big chance this was for me and the various things I was/am doing.
Using the same sound at home as on the gig? For me, that's pretty much the most fantastic thing. No, the sound isn't always literally 1:1 identical, Depending on the venue I might use a different IR (and yes, I'm always only using one per gig for good reasons...) or reach for a global EQ, but I'm at least used to a) my board (and how to "manage" it) and b) to the core qualities of my sounds. I just know how all the different dirt flavours feel under my fingers, simply because that's what I'm using all the time when playing. There's no home/practice amp nonsense anymore. Gawd, how much I hated them. There's also no more "great to fool around with at home, useless for gigs" PODs, VAmps and what not anymore, no, the stuff I have under my fingers as soon as I pick my guitar up is absolutely live-worthy.
Add to this all the mentioned silent stage situations. In case you never play silent stages, more power to y'all. I seriously wish I didn't have to - because as much as I enjoy modeling, I also like good stage (just that my amp is now replaced by a wedge, but it's still a physically separated thing). But then, using modeling all throughout defenitely makes silent stages much more enjoyable, because after all, it's at least the same sound I'm using at home.
Anyhow, you need to be persistent (and somewhat resilient, too) when checking out these waters. Unfortunately, at least for live, there seems to be pretty much no instant gratification.
And as a tip: If you have good reasons to go the modeling/DI route often (or even permanently), I recommend to not switch to oldfashioned amps/cabs in a while. Speeds up the process of getting used to things (at least it was like that for me). And who knows, one may find it weird to return to amps after a while (at least it was like that for me).
