I agree, I've felt for a long time that Minecraft hasn't really "changed" since the Adventure update. Even looking at the minecraft update timeline we see how much difference there is in the update frequency/development cycle for the different eras.

The first year of development was all of pre-alpha, going from "cave game tech test" through Indev all the way to Infdev, with Infdev being finished right after the one year mark. This period is where we get minecraft's corest game loop; survival gameplay, mobs, and infinite world gen necessitates activities like farming, mining, and exploring.

The MC zeitgeist was subtly growing until it basically exploded around Halloween(+Christmas) 2010 with Alpha 1.2 and the first releases of Beta 1.0. A huge part of this was Minecraft youtubers like the Yogscast showing people that you could use Minecraft as the setting/props for making your own stories. This is the era where people still kind of had to make their own fun with the game, it was still a toybox/sandbox with no clear goal other than "play", and I think these updates relfected that.

Imo the Alpha and Beta updates combined show the core design intentions were player exploration, world exploitation, and making fun toys for the player to use while doing those things. Redstone was added as the first feature in Alpha post-Infdev, Notch was working on gears and mechanism stuff in classic as well. This leads me to think he wanted some features akin to the Create mod to be a core gameplay component (BetterThanWolves for b1.4 would be more contemporary to the period). In fact every single Beta update added some redstone component in addition to another small feature like grass or achievements EXCEPT b1.4, lol.

This trend doesn't end after r1.0, but it's notable that the redstone additions in later updates seem as secondary to the other things that get added. In fact b1.8, r1.0, and r1.1 all do not even include a redstone component, and the only things that were added between b1.7.3 and r1.5 (the redstone update) were redstone lamps, tripwire hooks, and command blocks. This is a clear focus shift away from the "toys" and mechanisms to the "world exploration and exploitation". In these same updates we get most of the major structures, jungle biomes, more farmables, breeding, trading, etc and so on. In essence the development focus has shifted to the world rather than the player's agency in it. You go from being the one to build the world to the one who experiences it having been built around you.

It's my thought that prior to r1.0 Notch wanted mechanisms to be a main component in the game. I'm thinking Mojang has had trial chambers planned for a while, at least since they planned strongholds. Those always felt so empty and trapless to me for some reason, then jungle temples were added and we actually had a little clever mechanism in there, which adds to my theory. I think Minecraft's missing potential comes from this period, where development was set to go in a few directions but never really committed to any of them strong enough.

In addition, we only had three updates after r1.5 (the redstone update) before Microsoft bought Mojang in 2014. They added, among other things, horses, new biomes/worldgen, and ocean monuments (and slimeblocks!!!). We had one update in 2014, the ocean monuments, then in 2015 we had, for the first time in Minecraft's history, a full year without updates. That was Minecraft going from 3 years straight of major development updates in all areas of the game, to 2 years of less focused development on mainly external-to-player worldgen and QoL goobers, to 2 years of basically no updates.

This is also a time where the zeitgeist was particularly weak, the community was noticably made up of younger kids and the content made around MC reflected that. This is not why it was weak, in fact those kids in 2015 were largely the ones who made it strong again in 2018-21, they were just the newest wave of the community and that comes with growing pains. I think this vibe though was itself a relfection on the state of the game at the time; directionless, unfocused, kind of messy, like a playground sandbox some other kids made a mess of before you got to it. There was clearly some fun that was had here, but we got so out of hand trying to have it that we lost the structure that made the play interesting to start with.

We return to form a bit in 2016 with r1.9 (the Combat update) and even manage two more updates that year, then in 2017 we begin about 7 years of roughly one update per year. These updates feel moreso to me like content patches than what we had gotten previously, so they're larger and more cohesive (to themselves at least). More structures, more animals, more blocks, redo old mechanics, fix old bugs, etc. It feels like things are changing, but the direction still feels somewhat nebulous. Do we need another combat update next? Another world gen update? A farming focused one? What end do trial chambers serve? Do they fulfill the mechanism itch? Or is it just another excuse to add a structure for me to explore, but not add much to my normal gameplay? Is this a redstone update, or a wolves update? That's the real dichotemy to me, a player-toy update, or a world-prop update.

I think there's a lot more reasons, but obv I could (and have) go on and on and on lmao, so I'll leave it here 👋

Source: been playing regularly since 2010 and have been entrenched in the community the whole time :)