no @import for child-themes anymore?

Hello, i used child-themes for different websites and always used the @import method. And it alwayd worked fine! In fact, it is still working fine nowdays.

Now I know that it seems to be “good practice” to not use the @import method anymore, but instead the method as described in the codex, using an functions.php

I have searched a lot, but i can’t find the ansers to these questions:

1 – why should I not use @import anymore? what is the advantage of the new method?

2 – are my old websites, which are using the @import method, in trouble now or in the near future? Do I have to change them to new new method?

I am a WP starter, so please explain to me in simple words… Thank you very much!