This is the message you get not when there is NO disc, but when the console can't read the disc.

It's supposed to show up when someone puts in a non-playstation disc, like a PC game for example, but as consoles age this starts happening more and more with proper discs as the drive and especially laser wear out and lose performance.

So this basically means "your disc drive is dead or dying"

You sure can do that, but if the point is pure nostalgia, I think all that optimization defeats the purpose.

id imagine most people (should) be using a hard drive PS2 using freemcboot to boot roms off the drive.

the PS2 is definitely at the age where some disks may be getting disk rot.

I've done my share of console software mods, but PS2 was one of the more confusing ones for sure. From what I remember, the HDD loader is the most recommended method, but it requires either a drive with an outdated connection that mostly is not manufactured anymore or another hardware mod to make it compatible with SATA HDDs. You also need to format it in a way that makes it a huge pain in the ass to load games above a certain size or you can use a modified version of the loader on the PS2 firmware that can read NTFS formatted drives, but is harder to find guides for and I believe some PC-side tools are incompatible with it. I also experienced multiple unexplainable bugs throughout the process. I fully gave up after failing to get box art and widescreen cheats working on my modded PS2 and just emulate on Steam Deck instead.

But even if all of this did work, the other poster is right; after opening multiple menus and picking a game from a list, it just doesn't actually feel that much like playing a PS2 anymore.