Mary's realization about how unfair she has been on George in Young Sheldon season 4 finale makes her version in The Big Bang Theory worse. Missy's boy problem led to her and Sheldon's argument in the episode titled "The Wild and Woolly World of Nonlinear Dynamics." But after the pair had already patched things up, their original fight resulted in another conflict back at the Cooper house with their parents, and given how the rest of the evening panned out for Mary and George, the heated discussion became way more serious than just handling their kids' squabble.
Indirectly, Sheldon's stories about his father in The Big Bang Theory also depicted George as a bad husband. The socially inept genius even revealed at one point that all his parents did nothing but quarrel, hence why he didn't like it when Leonard and Penny get into an argument as it brings back memories. While the Cooper parents do have some conflict in Young Sheldon, their relationship is a far cry from what their son had described in his adult years — at least thus far. But as the prequel series continues, cracks George and Mary's marriage are starting to subtly show, which could ultimately lead to a more contentious dynamic at home just as Sheldon remembered.
Mary corroborated her son's stories by doubling down on them; she barely missed an opportunity to badmouth her husband, even though he was at this point long dead. However, acknowledging that she's partly to blame for George's personal misery in Young Sheldon season 4 finale highlights that her criticisms of him were uncalled for in The Big Bang Theory. In the prequel's finale episode of the year, George and Mary initially got into an argument about handling Sheldon and Missy's conflict. Their fight became personal, however, leading to George running down all the big compromises he's done in his life to make Mary happy. As he left home to let things cool down, Mary briefly admitted to Georgie that she feels frustrated about herself because she's one of the reasons her husband feels miserable. This does not only acknowledge that George was in fact a decent family man, but also that Mary's comments about him in The Big Bang Theory were below the belt.
To be fair, there's an argument about how the Cooper matriarch's constant criticism of her dead husband in the original show might have been because of his eventual infidelity. It's still uncertain how Young Sheldon will tackle George's cheating plotline although the season 4 finale could be an indication of the dark path for the character moving forward. Still, considering how long it had been, coupled with the fact that Sheldon's adult friends in Pasadena didn't have any personal connections to George, she could've decided to not say mean things about her dead husband.
While The Big Bang Theory depicted George as the bad parent while effectively making Mary the better parent, Young Sheldon is revealing that the situation is more nuanced than that. The Cooper patriarch will expectedly commit adultery in the future if the sitcom honors the previously established continuity, but thus far George is not a totally bad dad and husband as evidenced in the first few seasons of the period sitcom. Meanwhile, Mary isn't the perfect mother as she tends to be biased for Sheldon, as correctly pointed out by Missy, and self-centered as her husband mentioned.