As I've noted, I think that due to its tragic history of a long period of Turkish rule, the Greek script still has a serious issue with the integration of its upper and lower case, at least in serif forms.
With Cyrillic, I think the basic letter forms are sufficiently well related to those of the Latin script that there's nothing really inappropriate, nothing really contradictory to Slavic culture or the genius of the script, to simply take any Western typeface and adapt it to Cyrillic and use it routinely.
That is not, however, to say that it isn't desirable to go back to the roots of the Cyrillic script for inspiration in designing new typefaces, particularly for use by Slavic speakers.
Given that Times Roman came out in modified forms for German and French, why couldn't typefaces be modified to round the Er when used for the Cyrillic script? Obviously, it wasn't done because the typefaces in use in Russia (and Serbia, and Bulgaria, and so on) for the most part didn't have a rounded Er. I have to conclude from this that a rounded Er looks old-fashioned, and is acceptable when a typeface is to suggest a connection with the roots of the past, but is distracting in normal use.
Since excessive nationalism can be harmful, a shift in Russia's outlook and priorities that would lead to a change in tastes in this area might be a bad thing. But it doesn't have to be, of course. Countries can focus on what is positive in their culture and traditions, but a focus on them naturally tends to lean towards exclusivity as well.
And the world's traumatic experience in the Second World War has given culture and traditions a bad image, and other recent political developments seem to leave ideas of modernity and progress as the only positive alternative remaining. That, of course, is an illusion, because preserving what is of value in a cultural heritage isn't inherently bigoted or aggressive. But when dark forces are about, more caution is needed to avoid a traditionalist movement being co-opted, or for the innocent to avoid being confused with such forces.
Thus, with Putin invading the Ukraine and co-opting the Orthodox church to encourage Russia's people to support him on his road to disaster, I would be inclined to let those aspiring to show themselves to be his most loyal supporters try to reintroduce the rounded Er, and help to make Putin laughable thereby. Giving the rounded Er a fair consideration... is a thing for happier times.
I regret to have to drag politics into this, but while legibility is objective, aesthetics is not; people prefer different typefaces often because of their associations, and thus the merits of the possible associations are relevant.