I've written and deleted this post like 4 times trying to figure out what to say without offending someone. For good or ill, I have to resort to GNS terminology, but I promise to use it loosely and perhaps incorrectly

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D&D has always had a tension between Gamist and Simulationist concerns.* "Balance" usually seems to mean "intra-PC fairness" to most people. That's a generally Gamist concern. (I wish to be clear that I use "gamist" in no way derogatorially.)
The older (pre 3e) editions were horrible mish-mashes of mechanics, that somehow managed to barely allow you to run an rpg game. Gamist, Simulationist, and Narrativist ran headlong into each other. The primary methods of bending to one or the other were houserules. (I say this with great fondness. 2e narrowly edges out 3e as the edition I had the most fun with, in my heart.)
Now, IMO, 3e was arguably the most Simulationist version of D&D. This makes sense, given the state of the gaming world when 3e was designed, but that world changed during the course of 3e's reign. By the end, "min/maxing" had evolved from a sinful lowbrow activity to an accepted or even encouraged virtuous activity called "optimization." Since 3e had never really been designed with Gamist considerations in the forefront, this lead to what many saw as hideous imbalance. (Groups that were, perhaps, slower to adopt new attitudes might not have ever noticed a problem.) Certainly, imbalance became the rallying point for complaints about 3e.
So, when its designers sat down to make 4e. Gamist concerns rose to the top, riding on "balance". They did, AFAICT, a fine job. They created a very finely "balanced" game, with transparent, easily demonstrated, and fairly rigidly enforced fairness, both between the party members, and between the party and their adversaries. It was, to be blunt, a tremendous swing from the Sim end of things deep into the Gamist end of things.** The differences in feel at the table are profound.
Maybe a little too profound. The edition war erupted...maybe the less said, the better. I will just say that by the end of 3e's tenure, players and groups had subtly and slowly become divided over which side of the Sim-Gam axis was more important. While some groups saw 4e as a welcome breath of fresh air, others saw it has a horrid betrayal of the game they loved. Personally, I found it a bit of a wash. I have troubles with both sets of rules, and there are things I like about both as well.
So what, if anything, does this mean, for 5e? Simply put, that it needs to meet somewhere in the middle. PCs have to be playing in the same arena with each other, but they don't need to be clones. 5e has got to stop the "swinging" from extreme Simulationism to extreme Gamism, since that's at the root of the edition wars, or it will have no hope of uniting the playerbase.
An open question still remains: "Does the playerbase want to be united?" The possibility exists that most D&D players fall, not in the middle of the G-S spectrum, but at the extremes. In this case, reunion will be very difficult indeed.
Anyway, that's my thinkin' on it. Play what you will.
*Narrativist emphasis has waxed and waned slightly over the years, but D&D seems to mostly not know how to actually handle Narrative things. Instead, D&D has left most of that to either emerge from play or to be the direct result the DM putting his hand on the scales by fudging die rolls, etc. Exactly who has narrative authority over what is often unclear.
**Don't believe me? consider the oft-uttered complaint lines: "It feels like a board game.", "All the classes feel the same.", "How do you knock a Gelatinous Cube prone?" and even "Its a fine skirmish game, but not D&D." Consider also the constant threads about LFQW, and what points ring true for you and what points don't. Keep in mind that most of these changes are relatively Narrative-neutral, mostly because D&D is so mechanically Narrative-poor to begin with.