How common is it for people in Russia to have Visa / Mastercard....? I have heard that a lot of people just don't have it.
99% of companies that pay salary legally pay it on debet cards issued by V/M

Do people mostly have debit card (just withdraws the sum from your bank account) or credit cards (you spend money you don't actually have, and pay it later)
Mostly debet. Some with overdraft.

Would you consider it a serious problem if you couldn't use your Visa / Mastercard.
I consider it a huge win.