The ideology of minimalism
There's a lot of bullshit flying around that minimalism is something it isn't, even pointing to examples of egregious bloat as somehow "minimalist".
They're not entirely to blame because this is a profound and nuanced topic. Minimalism is a maximally general philosophy, with applications to every field, but unlike other grossly polymorphic ideas like "unity" and "diversity", minimalism rings true; there is a consistent thread across it all, and even more profoundly, it's consistently a good idea.
As for exactly what the idea is, I would say it begins with understanding that the practical cost of complexity is drastically higher than non-minimalists think.
As for what exactly "complexity" means: I don't think there is a precise answer to that. Instead of some exact ontological characteristic, I think it must be understood as referring to mental models, how difficult something is to understand, to explain, to remember, to recreate.
Why do I say "it begins with" instead of "it is"? Because after enough time it overflows that box. When you pursue the beatific minimalist vision long enough, it becomes a part of your very emotions, your sense of beauty. And I'll even admit it's possible for this sense of beauty to overstep its original motivation, become a hindrance to practicality. I know people to whom this has happened. I may even be one of them.
But I don't it's very meaningful to discuss minimalism in abstract terms alone. If you seek to really understand, to see its beauty the way I do, you must look at its manifestations.
Minimalism has many applications for software. Less code is better. Less programs is better. Less features is better. Reusing existing components is better.
Some benefits of software minimalism are obvious to anyone who knows even a little bit about the field. One obvious one is performance: less code runs faster, a program with fewer features starts faster, fewer programs take up less space on your disk and network connection (while downloading and upgrading them). As a direct corollary, it's better for your battery, and for your utility bills (albeit that's very small).
One that requires equally little knowledge, but is more subtle, is learnability: more programs and more features take more time to learn, clutter the documentation, and are similarly easier to misuse.
Two that require slightly more knowledge to see are stability (lack of bugs) and security: more code, more features, and more programs means more bugs (because it's harder for the programmers to avoid it), and more exploits for the same reason.
Developed minimalists like me, for whom minimalism is also a matter of beauty, derive joy from finding unnecessary things and deleting them, and intense sadness from learning that something bloated is necessary.
Minimalists generally dislike decorations, but this doesn't mean we have no sense of visual beauty or that we hate color. Remember that minimalism is ultimately rooted in practicality. The visual complexity of nature costs nothing, and colors, even on physical objects, cost close to nothing. But we do hate clothing, architecture, and software that sacrifices practicality for aesthetics.
Consumerism being defined as obsession with buying things and blindness or apathy toward the environmental damage and shitty practices that go into them and the fact that you empower harmful social structures by buying them. Thankfully there is already a widespread anti-consumerism movement and this is a crucial application of minimalism. A minimalist buys as few things as possible, by asking if they really need them, and knowing that the answer is almost always no. They reuse existing items, give them away instead of throwing them out or get an old spare from a friend instead of buying a new one.
Perversely, a common buzz in politics is about "creating jobs". At least it was when I was a kid. I haven't seen it as much lately. Well, fuck your jobs! A job is by definition a problem, not a source of wealth, you window-breaking asshole! You don't spend a job on a person, people spend themselves on jobs! If you can destroy a job without spending a person, then that's what ya fucking do!
Minimalist philosophy on language was described well by George Orwell's essay Politics and the English Language. In summary, minimalists write in a much more direct way with fewer words (we would never say "create interference" instead of "interfere" or "be dependent on" instead of "depend on"), and it makes our writing easier to read and more powerful.