Most of my time playing and reading RPGs has been ruled by the “undisciplined pursuit of more.”
I played several RPGs and took pride in trying new ones. I favored "universal" systems where I could create endlessly detailed PCs and do anything I wanted. I also collected monster manuals for my D&D-ish needs.
This process has been somewhat useful in helping me discover my tastes and needs.
However, there has also been much waste. I read only a fraction of the RPGs I buy and play an even smaller fraction of the RPGs I read. Nowadays, I'm embracing "the disciplined pursuit of less."
In other words, I want less: fewer monsters, fewer spells, fewer magic items, fewer stats, and simpler systems.
This partly reflects my appreciation for minimalism, but it goes beyond that. I believe that having fewer elements makes each one more important and meaningful.
While having a multitude of monsters is fun, each Monster Manual contains more creatures than entire worlds like Middle-earth, Barsoom, Lankhmar, or the Hyborian Age (not to mention most horror and sci-fi settings). It becomes virtually impossible for PCs to understand each individual monster with any depth.
Take dragons, for example. The dragons of mythology and literature are often unique individuals, like Smaug, Fafnir, Tiamat, Drogon. Each is distinct and memorable. But the 2e MM (my favorite!) has about more than a dozen dragon types. If a D&D party sees Smaug, it is just another red dragon (they don't even need to interact to know that he is chaotic, since he is red; but this is another issue).
[Another thing I've been considering is how adding more monsters to a game doesn't make it any different from "standard" D&D, but replacing existing monsters creates a completely new kind of setting. Take Curse of Strahd, for example: it includes few "demihumans," and even the elves are distinct from the familiar elves we're used to. This seems to hold true for most of my favorite settings and modules, and I think I might never run an adventure containing orcs again.]
Magic items are the same: Excalibur or Stormbringer are memorable, and so is Sting. In D&D, a first-level party often has dozens of magic items. Eventually, they discard some of them as they reach higher levels. This abundance devalues magic items and magic in general.
I feel the same way about rules.
I’ve run a few 5e campaigns. 5e is a more "complete" game than B/X. However, it requires ten times the page count to achieve this. So, I’ve been asking myself: is 5e ten times more complete than B/X? And the answer is no. Same goes for AD&D.
[Sure, I could use a one-page RPG. In the end, this ultimately comes down to a matter of taste.]
Spell selection has also been a headache, leading to imbalance and analysis paralysis.
I like customizing characters, but I don’t need dozens of classes and races. I really enjoy the simplicity of being able to say the bandit leader is a "fighter 5" and leaving it at that.
When you have fewer elements, you can connect them more meaningfully. For example, elves resist ghouls. The undead are raised by demons. All aberrations come from other dimensions, while monsters are created by mages. Etc.
And to be honest, this would make way more likely that my players would even REMEMBER most of this stuff.
In short, many of my current issues with D&D could be solved by just having less.
Additional reading:

