It's sad and funny to see "Russian supporters" arguing that Soledar is a "city" . You might go to wikipedia and see the population numbers:
10k people in my country is not a city, but call it whatever you want. The important question is the main defense line after 2014 is behind Bahkmut, western part is full of flat lands where Wagner offered the lives of thousands of people to advance a few kilometers.
As we have seen the number of people matters, and the mobiks who are part of original RU units doesn't have the performance Wagner had with their tactics and morality. You can see Vuhledar offensives, canceled by "bad weather" when there is a shining sun every day, and it's just a small village being attacked by original RU units and mobiks.
So for reaching Kramatorsk and Sloviansk, RU would need to conquer Kostiantynivka and Druzhkivka, which are behind the main defense lines, and being prepared for many months for the defense.
Even if Wagner is able to gather hundred of thousands of convicts, insanes, etc. They might reach those cities in many months or even years, time enough to have plenty of main western weapons in the field.