In an era where we have access to the NES library via Nintendo Switch Online or mini-consoles, why bother with a clunky "400-in-1" ROM?

This is the grey area. Let’s be direct:

While emulation technology itself is legal, distributing copyrighted ROMs is not. Abandonware:

: While many games on these carts work well, battery-backed saving (essential for RPGs like The Legend of Zelda ) is often hit-or-miss depending on the specific hardware build of the multicart. Performance & Quality