I’m assuming you’re talking about nutmeg which was today. To answer your question yeah cat 5 crits are going to be pretty fast like that. Just for context when I’m riding fast on the road I can do maybe 23ish depending on the road profile. The key to keeping up in a crit is following wheels and cornering. There are always going to be strong guys near the front able to drive the pace.
anyhow yeah working on fitness always helps, I don’t think your weight would have factored in at all on a crit like that, and the key is just to keep going out there and trying to hang on