Non-moldable liners are perfectly fine if you're just starting out and only skiing a few days a season. They come standard on entry-level boots and will gradually conform to your foot through regular use, so you'll still get some break-in comfort over time.
The downside is they offer the least customization and tend to pack out—meaning they compress and lose their shape—more than heat-moldable options. If you have fit issues like heel slip or pressure points, there's not much you can do to fix them since these liners can't be heated and reshaped.
The good news: if you catch the skiing bug and want better performance later, you can swap in an aftermarket heat-moldable liner like an Intuition without buying whole new boots. It's a worthwhile upgrade that can breathe new life into a budget boot.