But I agree: using more memory is good, actually, because it means more stuff is being cached. Nautilus is probably pre-indexing directory structure so it doesn't have to read disk every single time you open your home folder. That's good. Oh, and thumbnails. Thumbnails are incredibly expensive memory wise, but very useful!
Also modern apps have A LOT built-in. Tons of font management stuff, accessibility, they work on many different environments. I mean, look at everything that goes into a modern terminal emulator.
But... a weather app is much simpler, IMO, than Nautilus or Kitty.