Perplexing user experience, nothing works

The user experience is very perplexing. I downloaded the latest Windows stable version, launched it, downloaded a core, so far so good, but then nothing works:

• I tried the Mac II (minivmac) core and the whole program just gives up and quits. That doesn't look like a typical crash to desktop, it seems more like someone put a exit(0); somewhere and that's it. The same thing happens with Commodore - VIC-20 (VICE xvic). Why does it quit? No way for a user to know.
• I tried Amstrad - CPC (CrocoDS) and this one fails the hardest, it doesn't even try to do anything, it just goes back to the main menu, and the "Start Core" button is gone! So clearly that core is very broken, but then the same thing happens with Arcade (MAME - Current),Atari - 2600 (Stella), Atari - ST/.... You'd think the program would alert the user that the selected core cannot be started, but no, nothing of the sort, you're just left noticing that the "Start Core" button is gone.
• I tried Palm OS (Mu) and it just says "Failed to load content". Now I'm sure there's a good reason for this, such as needing to install some extra files, but this is the core of the perplexing experience: you make it easy to casually download and launch a core, but then it does nothing except show a message that provides no explanation nor pointer to an explanation as to what should be done. What's the point in making it easy to download a core if when it comes to being able to do anything with it you're left on your own with no indication of what you're supposed to do next?
• I tried Microsoft - MSX (fMSX) and I just get a black window. What's wrong or what should be done is even less clear, it's just a black window.
• I tried Cave Story (NXEngine) and I get both "Failed to load content" and "NXEngine game files missing from frontend system directory". That's more than fully unhelpful, but what do I do then? What files do I need, where do I get them and where do I put them? Is there a webpage out there that explains it? Well then maybe maybe a dialog with a button that opens the URL to the page that explains what's needed.
• I tried Commodore - C64 (VICE x64sc, accurate) and oh this one technically works! Except it's utterly unusable because as I tried to type 10 PRINT HELLO only 10 prints then the other keys act as shortcuts, P pausing the emulation entirely. I'm sure there's a way to make it usable, but how would I know, clearly none of the menu items have anything to do with this problem.

Note that this is an exhaustive account of my experience, I didn't leave out any core that I tried, truly nothing worked. I've never seen such an extreme level of nothing working in a program. Some programs are unusable because of a couple of bugs, but here you have all these different ways of totally failing, and nothing I tried actually worked.

Start by reproducing the reported behavior in the Windows stable version with the listed cores, especially the cores that quit, return to the main menu, show "Failed to load content," or open a black window. Compare the visible behavior and messages across those launch paths; done should mean users receive a clear explanation or next step instead of silent failure, unexplained errors, or unusable input.