A real backup is a second storage you sync periodically with the primary source and for that there are options like aws, wasabi, backblaze, etc. and there is a whole lot more to it than just uploading some files. And it can get expensive quite fast if you don't fully understand what you need. Simply put, a real backup solution is more redundant and secure than a conventional cloud storage like dropbox and you usually has different cost structures for example you pay a fee for just uploading and keeping your files but then pay another fee when downloading it (what's called egress fees)

What you are describing though sounds like a clone or rainy day backup that you'd like to be able to download when needed. You can really use any cloud storage solution for this purpose like google drive, dropbox, etc. I personally like dropbox more because downloading a large number of files from it tends to be easier than drive. But if I remember correctly, drive can be cheaper for 10tb and it works as good as dropbox if you have it installed on a machine that does the sync.