Thanks for clarifying your intent! (For reference, to me the term "play-acting" comes across with an inherently demeaning context, especially when things that affect the "play-acting" level of the game are also described as "superficial".) To further clarify, do you think the "play-acting" level of the game is important and something to be encouraged at your table? If so, that didn't come through--it sounded like you don't prioritize that part of the game, or value the characterization that takes place there, even though you take part in it.
No, I don't feel it's something that needs to be encouraged. If you feel like it, go for it! If you don't, third person's fine. I don't feel that roleplaying is especially enhanced by play-acting -- it's one way to do things, but it's not superior or better, it's just different. You can roleplay very well in third person. Personally, I enjoy it, and most of my table enjoys it as well, but if someone's having an off night and doesn't want to do silly voices, that's entirely cool -- we all roll with it.
I think 5e is often labeled as flexible in comparison to other editions of D&D that (arguably) catered to a more specific playstyle. I think that's a worthwhile comparison to make, even if it is limited in scope.
This is the narrow version of the argument, though. The broader version, where 5e is upheld as able to do many types of play (see
@Oofta) is also very common. I'm not sure I agree with the narrow argument, though. 5e isn't more capable of different approaches than 4e, for instance, which could actually break out of the traditional approaches and go into a near-Story-Now play mode, which is very different play! It's not more capable than 3.x, either. The only difference is that the advice for 5e isn't as rigid as that provided, and the zeitgeist is more open, but, again, it doesn't reach places the prior editions could not, it's just less constrained in it's presentation. It can't really do more than you could with 3.x, unless we're talking about ignoring the system when it's convenient, and then we're back to the same place because you could do the same thing with 3.x.
I can see how you feel that calling something flexible within such a narrow scope lacks broader relevance. However, I would point out that only using a universal scale to measure flexibility has the drawback of restricting one to high-level comparisons. That's great for high-level game design theory, but that's usually not the level I think most people are operating on when they say they like (or appreciate) 5e for its flexibility.
I'm still not sure what accounts for 5e's flexibility in your argument, though. How is 5e flexible? What can you do that's so different, in your opinion?
Maybe we just encounter people making the claim that 5e is flexible in different contexts?
My context is EN World.
To clarify, I prefer to emphasize (what you are calling) play-acting for the players as a goal of play at my table. I did not intend to imply that I also emphasize designing characters who play-act IC.
At the same time, I expect that many character traits will often be expressed primarily in the "play-acting" level of the game. That doesn't make those traits superficial, from my perspective, or imply that the play-acted characters are themselves merely play-acting.
I find that if an Ideal, Bond, or Flaw (Traits are pure fluff, and very much grist for the mill you suggest) is only present in play-acting, ie, the player giving lip service to it while acting out at that table what their character says, then they're not worth much at all. Funnily, this has been my point all along! If you're just using these as prompts for the improv acting you're doing at the table, that's cool, but there's no there there. This is superficial, because it doesn't drive the character in any way, it just prompts the player to say some words in a silly voice (or not, I don't know if you like silly voices -- I do). To me, if a character has an Ideal, that shouldn't just get lip-service in the improv theater, it should be something that actually defines the character through action and choices. And those aren't play-acting, even as they might provide prompts for play-acting.