Not really comparable, China's goal back then was just to take uninhabited border territory, inflict battlefield defeats on the Viet army and sack some cities.Ukraine war at present reminds me of the 1979 Sino-Viet war.
One month earlier, many people were mocking China had no military action in Taiwan. A retreat not mean the RU whole failure. I will not laught at Russia until the end of the war and observe what will happen next.
And some people mocked China back then because their goals were so modest instead of trying to annex large parts of Vietnam. But because of modest goals, they didn't get bogged down and avoided high losses.
Russians on the other hand have no choice but to get bogged down. They fully intend to steal large parts of Ukraine.
If Russia thought they could do that without mobilizing, their leadership was greatly mistaken. But if they are just softening up Ukraine for a full scale blitz using the whole Russian army later, then they're more or less on schedule. Towns switching sides then is not a huge concern. As long as Russia doesn't lose much men and can make a new, actually stable defensive line at Oskil and keep making Ukraine pay severely for every advance.