That doesn't quite make sense. Most DVDs are encrypted, region lock is implemented in DVD encryption, that is usually the problem encountered by most ppl, especially regarding imported discs. But you claim it's not region lock issue...
It could be that Win 10 doesn't come with the decryption code/key just so Microsoft can save a couple dollars on license fee. I might have encountered this problem some years back with a brand new company laptop. What I taken for granted (DVD playback) was unavailable on the system out of box. I searched around and found that many commercial software bundle the code/key for decryption, but had to dug around more to find a free (could have been cracked software I can't remember) version.
Sorry seems you aren't getting the help you need. Because hardly anyone have that problem. When I buy a disc, I rip it once and make an MP4 out of it, and then put the DVD in original case away for long term storage.
I believe VLC player is a fine "container" app, but for playback (like all media players) it relies on codecs which might or might not have been bundled.