They are better than nothing, the main point is to activate your feet while walking/training. Having more cushioned shoes makes it more difficult to activate/use your foot and ankle muscles, so in that way vans are better than most shoes having low cushion. But the soles of vans are generally fairly inflexible, meaning your foot can't move through that natural motion as easily.

If you can train barefeet, or in socks, go for that. Otherwise water shoes are usually available in most countries quite cheaply. Something like this I don't know anything about that specific shoe but that type of shoe could work if it's available cheaply. Only problem is that since they are designed for wear underwater, the material might be thicker leading to hot feet.

If you do your foot and ankle exercises (barefoot!), and try to consciously activate your feet while walking/training. You'll still improve your feet wearing any shoe.