And Iosue , as the one that piqued my interest, I would be especially interested in examples you could give.
I certainly think the process has been a gradual one, and if you've been involved in the game constantly through the years, you might not notice it. Late 2e's Combat & Tactics and Skills & Powers flowed more or less naturally into 3e, and late 3e's Book of Nine Swords flowed more or less naturally into 4e. When I look at the rules for 3e, I see something that recognizably TSR-era, as well as something recognizably 4e. So let me stress that I by no means think of 3e or 4e as "not D&D", despite feeling unfamiliar with the new terminology. It's been 25 years since I started playing, so of course the game is going to change and evolve, and I hold no resentment for the folks who first got into the game with WotC-D&D. Unless, of course, they start putting down the D&D of my era as "out-dated", "poor designed", and so on. Nor am I at all unaware of the differences between the D&D I grew up with in the 80s and 90s and the D&D of the 70s.
That said, here's where I see differences.
First of all, any talk of charop immediately throws me out of my D&D language comfort zone. Particularly with 3e (but that's only because I'm familiar with 4e). When a conversation turns to builds, or 3e caster imbalance, I quickly lose the whole thread of the conversation. As mentioned earlier in the thread, talk of tiers, dipping, gishes, multiple ability-score dependencies, and so on, is simply not something I ever associated with D&D back when I played from 1987 to 1998.
But the differences also go more fundamental. We didn't "build" or "optimize" characters, we "rolled them up". In my day, we talked about "to-hit matrices" and later "THAC0". Now they talk about BAB (if 3e/PF) and Base Attack Roll Modifiers (if 4e). So I say "to-hit roll", but now people say "attack roll". Saves, of course, are a big one. When I think of saving throws and D&D, I think of vs. Death Ray, vs. Polymorph, vs. Dragon Breath, etc. Nowadays, save means Fortitude, Reflex, and Will. Or those are Non-Armor Defenses, which is another term I never associated with D&D.
When I played, a "turn" in D&D was 10 minutes of in-game time, during which PCs moved at a certain rate and a turn sequence was followed, and a "round" was 10 seconds of in-game time, during which PCs moved at a separate rate, and a combat sequence was followed. Now a "turn" means the actions each player respectively takes in a round, and a "round" means going through the full initiative order. On a related note, in my day "initiative" referred to being able to go first in a battle. Now it refers to the order of the individual participants.
We used to talk about "wandering monsters", but those are pretty much gone from the game. The "core four" to me are "cleric, fighter, magic-user, thief". Now it's "cleric, fighter,
wizard,
rogue". If I said, "My character is a Warlock," it meant, "My character is a 6th-level magic-user." Now it means, "My character invokes an eldritch blast through a pact with a supernatural being," and if you change that, people get upset. We used to buy "modules". Now people buy "Adventure Paths" and "splatbooks".
3rd and 4th talk about Standard Actions, Swift/Minor Actions, Move Actions, and Free Actions. People talk about DCs and CRs. Their characters take Feats. They make Spot and Perception checks (and note that I'm not saying those didn't exist in TSR-D&D; I'm talking about language). They make Attacks of Opportunity/Opportunity Attacks and either suffer or impose a host of conditions that I can never really remember off the top of my head. Sure, 4e has its powers and new mechanics like Healing Surges, but from my POV 3e has its Iterative Attacks, Level Adjustment/Effective Character Level, and a host of special abilities. Many of those special abilities existed in one form or another in TSR-D&D, but the way 3e presented them changed the conversation.
Both with 3e and 4e, WotC attempted to expand their base by appealing to gamers who were not, at that point, interested in playing D&D. For 3e, this meant going highly simulationist, rules-as-physics, with all sorts of ways to customize characters. 4e brought in a higher level of balance through mathematical precision, and features reminiscent of indie-games that gave players more narrative control. And while these moves may have been somewhat tangential to
my interests in D&D, how can I blame them? So more folks, who were at best indifferent to TSR-D&D and at worst actually disliked it, joined the D&D family. And as far as I'm concerned, welcome to them! I've had many an interesting conversation with folks with playstyles and expectations wildly different from mine. But they've also had an effect on the conversation.
The design paradigm of a disperse system that encourages DMs to add their own innovations and make their own case-by-case judgments is now called "lazy design". Game interaction through Player-DM give-and-take is now called "mother-may-I". The primary thrust of 5e design is, "We want you to be able to adjust the game to play however you want, be that grim and gritty or horror or high fantasy." In the 80s this was taken as a matter of course. Now this has been called "incoherent". All the D&D books I read in the 80s, from B/X to BECMI to AD&D advised to use fudging as a tool. This is now a vehemently reviled strategy. We talk about "sandbox" and "railroads". Again, I'm not saying that such differences and debates didn't exist back in the day, but the language has changed, and with that change I do think battle lines have become a little more defined.
And let it not be thought that I'm saying all the change has been for the bad. Back in the day you heard the terms "roleplaying vs. rollplaying", "munchkins", "min/maxers", "Monty Haul", and with the attendant smug superiority. Those terms have generally fallen out of use and out of favor. You hear them from time to time, but it's no longer the mainstream to put down the playstyles those terms contemptuously referred to. New terms, like "badwrongfun" and "One-True-Wayism" have come up, and I think for the better.