Yeah discord is not the best for file sharing unless everyones on the same channel.
Cloud storage is prob the easiest way to exchange files.. eg most people have a google account either due to an android phone account, a youtube account or a chrome account which all comes under google and if you've got a google account then that means you've got an unused google drive account with like 5-10 gig on it which you can drag and drop files into and then share with others.
If you have a microsoft account or you have an old hotmail or windows live account then that means you'd have a unused onedrive account with around 5 gig on it which can be used in the same way.
Dropbox is another popular one too.
All are free, all easy to use, all have gigs of storage for sharing files, and most people likely already have one or more of them without realising it haha.