This is just partly true. Most new exhibits in Russian zoos are very expensive, just like the one for polar bears that contains soo much concrete that it could hold a Tyrranosurus easily. It is a nightmare for bears and will cause high stereotypy, whatever you do to "soften" the inside. Why on Earth someone decides to build a monster? Russian people now travel easily and a lot to other countries. Don't they see what is going on in foreign zoos? Or is it just an arrogance? The cost of entrance can easily be raised if zoos would really change and provide better surroundings for visitors. Look at the numer of people employed there. It is usually double or triple numer to compare with similarily sized institutions elsewhere. I think the zoos need first serious structural changes.
I don´t agree that European zoos should boycott Russian zoos and refuse to send there their animal, this way wouldn´t bring any improvement at all, and it would just lead to increased stream of wild-caugt animals. Better a surplus zoo-born animal then a wild one, even if an eclosure is far from an ideal. But I do agree that zoos that send there any animal should always inspect the future living conditions, refuse the really bad cases, and provide experience/tips for enclosure and professional skills improvements.
I still have hope for Russian zoos. Russians are avid zoo visitors (Russians are even the most numerous tourists that visit Prague zoo). Russia is getting richer and as you mentioned, they travel a lot abroad. All it needs is an enthusiasm of the zoo workers there and a structural change in a way those zoos are operated. And especially good zoo directs.
I have read memories of Czech zooworkers from the time of Velvet Revolution when we finally liberated ourselves from Soviet occupation. In the first months after borders to Germany and Austria opened, they took cars/trucks and in drowes pilgered to DE/AT zoos, to see them, to make fotos of enclosures and to make contacts with those zoos. And Germans/Austrians were in most cases extremelly helpfull. They took them on inside excursions, answered all questions, donated a lot of literature or older equipment, often provided free rooms and meals during those visits etc. Czech zoos had hardly any money then, but many improvements could be done immediattely on very low budget.
What I lack a little in many Russian zoos is this drive or hunger for experience/manuals/tipps from zoos abroad. But maybe it is just my feeling.
The answer for Rostov zoo is probably lack of money, or unwisely-spent money.
Even a carnivore exhibit in Moscow zoo (Beast Island) which is dating 1930's is still more pleasant to look - besides the fluent shape of enclosures, the moats are sloping gradually so no risk of falling for animals. Bears were and are kept there.
Here are the projects of Rostov zoo's bear exhibits rendered in some architecture software.
As the zoo site shows, the most awful exhibit that holds Brown bears which are now switching with female Polar bear, was not planned at all!!!
Polar bear exhibit - looks at least not so ugly with those tiles, still a madness.
It's so tempting indeed to show Polar bears on ice (=concrete), just as they never experience other substrates in the wild.
The zoo site says that this exhibit was planned for Asiatic black bears.
Only adjacent Sun bear exhibit was built (look for cone-like structure at the far right)