If they were within the EU they would be. But because Dimitry is outside the EU, whoever's importing their work from outside the EU is responsible. (This prevents avoiding VAT by having your work done outside the EU). The EU has no way to go after an outside entity, so that's how it has to be.
Maybe I'm not quite intelligent but doesn't the VAT only work in the same jurisdiction? I mean, if we are on different tax jurisdictions then VAT should not be applicable. That's, at least, how it works in my country.
Right, if I (in the US) buy something from Krita that was made in Russia: Kritia needs to pay the VAT when they buy the work from Russia. Then when they ship to me they get a refund of that VAT. The sum collected is zero, but a lot of paperwork had to be done correctly to get there.
A simplified explication is Krita's situation is so complex nobody in the world can figure out how to get the paperwork correct, but they are not in trouble because they didn't. Tax law doesn't care if you can figure it out how to do it right, just that you do it right.
What do you mean by "work"? You don't get to just not pay VAT by having the transaction take place across a border. (At least, not when that border is on the boundary of the EU).