Statistics can be deceiving. Rybakina has a really powerful and effective serve, but it doesn't come close to Serena's as far as overall quality.
This reminds me of when Kyrgios was saying how he didn't like playing mixed doubles with Serena because she wanted to do everything, including serve first. He said he was thinking: "Hold on. I'm better than you." While Kyrgios may hit a harder serve than Serena (obviously), he still has an inferior serve to Serena's because a smart tennis player would rather have all of the attributes of Serena's serve under pressure than Kyrgios' serve. I am talking about disguise, clutchness, free points, speed, placement, and variety.
Serena's serve is the greatest shot in the history of women's tennis, and there are several men who would have much better careers with Serena's serve. This isn't because it is the hardest serve that has ever been hit. The disguise on Serena's serve is unlike anything I have ever seen before. Also, the motion is the most fluid, which is why it was able to hold up for over two decades on the tour. Rybakina has a very good serve, but the motion could be improved. There is a slight lag between the toss and contact that if she smoothed out, she could get even more power on the serve.