OThis sounds literally exactly the same as the arguments I've heard, and even made myself, to people saying that 4e classes were "samey." That is, the difference is borne out through play experience rather than through reading. So...I can't help but see a significant irony there, telling 4e fans that the differences ARE "academic and meaningless," but the NEW differences in 5e are very meaningful.
There's at least two things wrapped up there that should probably be disentangled.
The first is that "it plays different than it looks" isn't always a convincing argument. It's fair that it's not convincing, but it's also almost tautological in games. The extent to which it is true varies and if you suspect it might not be true, it's pretty easy to test. 4e did generally work differently in play than it seemed on paper (for one, it was a lot less rigid in practice than it seemed). 5e does too. So have 3e, and 2e, and 1e, and OD&D, and....most every game ever. The degree differs. I find 5e to be pretty high on the "it plays different than it looks" scale - something I don't think I'm alone in.
Second is that this argument is being used to say that the classes in 5e aren't as samey as they may appear. The fact that I still saw 4e classes and many 3e classes as samey after 8-10 years and don't see the 5e classes as very samey after 6 months should tell you I have a high threshold for "samey" - a threshold not met by 4e classes or every 3e class that is met by 5e classes. Presuming I'm a reasonably rational actor here, one might conclude that the differences between classes in 5e could be more substantial than they were in 4e.
That first thing might be wrong, or that second thing might be wrong, or they might both be wrong, or they might both be right, and just because the argument was used in 4e and you didn't find it convincing doesn't mean it's not true about 5e, since they are different games.
What would you say it is that a Sorcerer can do that a Wizard cannot, or vice versa? That is, you've said that they're "VERY distinct" (emphasis in original)--in fact, so distinct that you have never seen a SINGLE thing to suggest that they're the same, instead a "wealth of counter-evidence" to that claim. What, exactly, is it that one can do which the other can't do, which doesn't get borne out on paper?
I mean, there is this thread with 5 pages of replies that goes into a lot of discussion about how/why/if they're different from a variety of perspectives. Notably, there isn't a
single vote on that poll for "really only different cosmetically," which I wouldn't expect if a lot of folks felt that the differences between the two came down to "paint."
As I pointed out with the ranger and the fighter or the bard and the wizard or whatever, the bulk of the difference lies in the impact of (sometimes seemingly inoccuous) class features.
For sorcerers,
sorcery points carry a lot of the weight for the class in general. This affects the dynamic of playing a sorcerer by helping the player to avoid the loss aversion of spellcasting - you have sorcery points, you can afford to convert them to spell slots in a pinch (notably you always have enough sorcerery points at a given level to be able to swap at least some of them into your highest-level spell slot, up until you get 6th level spells). You aren't as concerned in play with the conservative use of power, which goes on to encourage you to play a little more brashly and recklessly with your spells than a wizard, which ultimately leads to more spellcasting, which helps the distinction by making you a constant source of something magical happening, in pretty much any situation where you know a tangentially useful spell.
This is notably distinct from
Arcane Recovery, because AR only activates on a rest, while sorcery points can be used on the fly. You can start off the fight with a
fireball because you always have an ace in the hole if the fight is suddenly joined by a new wave. Other spellcasters need to more carefully understand the strategy of their spell-use.
Additionally, someone who isn't as loss-averse or who doesn't have as many encounters can use those points for metamagic, which encourages you to use spells in situations where you normally wouldn't, or to use spells more efficiently in more situations, again producing a spellcaster who casts spells more often. It also produces a spellcaster who manipulates magic in more efficient ways, which you'd expect out of a character who is born with magic in their blood (vs. one who understands it intellectually).
If sorcerers were INT-based and had the same spell list as wizards, those sorcery points would still remain a meaningful point of distinction, because they would result in more spells being cast by the character with them than without them, and/or those spells being distinctly changed through metamagic
On the wizard side, the big distinction is the
spellbook. It's a very short paragraph, and a sidebar, but it is probably the wizard's most distinct feature, because no other class has the possibility for the
variety of spells that a wizard does. Ritual casting enhances that by making a variety of spells more useful (not consuming resources). Because wizards can afford to learn nearly every spell they come across, they build up an assortment of effects and magical abilities that are useful in more niche cases, or if more time is taken to craft them. A wizard is your crazy perpared batman, always with the right tool for the job. They learn more about their jobs, they know more about the niche uses of spells, they don't let hyper-specialization bog them down.
If wizards were CHA-based and had the same spell list as wizards, the spellbook + ritual casting would remain a meaningful point of distinction, and would still lead to more magical solutions to in-play roadblocks. A wizard would still be a swiss-army-knife that a sorcerer just wouldn't be.