I enjoy using classic Mac OS, not because it's nostalgic to me in any way - I'm too young to remember anything before a white eMac running 10.2 or something like that - but for the exact opposite reason. It's completely foreign to me in how it functions. It does everything totally differently to what you expect from modern operating systems.
File extensions basically don't matter. They're irrelevant. What matters is the metadata encoded into your file, and if it aligns with the metadata certain programs expect.
Dragging a file from a removable medium like a floppy disk onto your Desktop does not actually move the file off the removable medium. It simply makes it look that way, if you eject the medium then the files disappear from your Desktop, and if you reinsert the Medium, your files reappear. This worked for the hard-drive-lacking original Macintosh, but it's absolutely wild they stretched this metaphor into the OS 9 era.
There is no visible default location on the system hard drive for user created data. No folders for "Documents, Photos, Videos, Music" none of that. You can create your own, of course, but it feels Wrong, in a certain way, like you're forcing your own ideas onto it. Where else are you supposed to store your files, anyway? Not here. The Macintosh HD doesn't want your files. Keep them away. This is for programs only.