The original intent of Unicode was great: a standard that creates a mapping between a unique number==codepoint and specific character of language (and here character means only abstract non-visual symbol==meaning, not visually rendered glyph with stylistic font of any kind). The updates for Unicode versions added more languages, even dead ones. So basically it was a historical knowledge effort also.

Then came emojis, and now the Unicode Consortium's efforts for Unicode version updates seems to be about adding more different kinds of poop emojis and shades of skin colors. Well, maybe it projects accurately the language and culture of this modern time.

UTF-8 is great because it is a superset of ASCII, but because its byte-width varies, it has more complexity for decoding/encoding it (similar to constant/variable width ISA's in CPUs).

Different languages have different concepts, e.g. text direction==flow (left/right, up/down, characters/logograms, different kind of visual cues etc.). Humans create problems when they want to combine different languages at the same time. E.g. mathematical notation is in my opinion 2D graphics, and it cannot be (usually/always) inlined with text glyphs (to be aesthetically pleasing). Same kind of problems may come when trying to inline e.g. languages with different flow directions. Its like trying to combine native GUI widgets in Win32 and Cocoa/SwiftUI and GTK/Qt/WXwidgets - the (visual) languages doesn't have the same concepts or they are conflicting.