There are two ways to interpret "minimalism" in the context of design: sparse and succinct minimalism.

Sparse minimalist design means using as few elements as possible, and sorting everything with special aesthetic consideration for composition so every element seems deliberate and purposeful. When done well, sparse design is like good editing: it helps the design feel spacious, and it directs our attention skillfully to the important bits. Because sparse minimalism specializes in composition, individual elements of a design can be simplistic in texture and shape (but they don't need to be). Bootstrap and Google's Material Design has helped non-designers to create good-looking plain sparse designs without needing to worry about texture or ornamentation which they're ill-equipped to handle, especially with web technologies which function better when left plain. Unfortunately, even decent design principles are wasted and ruined by non-designers, because having two specialties in a world of heavy capitalistic specialization is rare, and design is a difficult specialty. Worse, developers who have through practice become good designers tend to over-rely on the plainness of design taught by Bootstrap and Material Design.

Also, sparse design is often a lie. Sometimes, a product needs too many features to neatly fit in a sparse design. This leads to two horrible choices: sweeping functionality under a rug, or removing functionality entirely. Sweep-under-rug design is where a designer takes all the ugly bits of functionality and merely stuffs them within clean-looking menus—you peel back the rug and find option after option, just layered beneath layers of menu choices. Sweep-under-rug is a silly and mostly annoying over-reliance on minimalism where a more robust design would be more apt, but it's mostly harmless. The same cannot be said for the idiotic tendency to outright strip functionality in the misguided pursuit of minimalism, such as with mobile versions of sites, which leave users hunting for ways to disable mobile sites in favor of their desktop counterparts. If you do this, I get it, it's tough to fight social momentum, but now that you've had it pointed out as inexcusable, please stop. In the pursuit of weight loss you could decide to rip out your limbs—but let's agree that's no sound choice.

Succinct design means minimalism of purpose. It is exemplified by, among other things, the Unix philosophy, wherein a program should be expected to do a single thing well, and to interact in predictable ways with other programs. In contrast with stripping functionality, this design method is about baking in only a few features, whose use is maximized. Microservices are a good example of this notion.

Minimalism of function allows for the composition of larger, often unique views, and often is divorced from stylistic design completely. This could allow a user to customize the presentation of an app, and only include the functionality they intend to use.

Sparse and succinct design are not mutually exclusive, and neither are they strictly complementary. They are tools for the designer or developer to judiciously apply. Minimalism isn't a single philosophy—it isn't a single color of paint to be applied to every design to yield one result. Form and function are separate concerns, though both are intertwined in the context of design. Because of this, good designers should consider more deeply what they mean when they strive for minimalism, because it can to apply to either form or function, or to both. I know I sandwiched my opinion about zeitgeisty sparse minimalism in here, but my point is just to think about minimalism of form and function as separate things to potentially strive for, and... alright, I'll precipitate and add that I'm tired of Google-style plain design being conflated with minimalism of either type, and that I'm pretty tired of seeing it in general. There are more interesting applications of even sparse visual minimalism than plain design, and in general, I think functional minimalism is a better philosophy than the dogmatic Big Web vanillization of design.

To end in an utter tangent: cottagecore is the kind of busy, grungy, beautiful aesthetic that can happen only by discarding the practice of plain design. In cottagecore, the cohesiveness of the visual design doesn't depend on having limited palettes and shapes or unadorned wide spaces. Much like wildflowers, the beauty of cottagecore comes from the skillful mixture of colors, textures, shapes, and sizes. Much unlike Google and Twitter's tired UI styles, cottagecore doesn't hide that design is a nuanced specialization which should at least be approached with an air of humility by interested developers, and failing that, should be left to actual designers.