I think the first thing you should ask yourself is why do you think the workout you did is a good representation of what a crit is? I don’t mean that as a dig or anything but what you described doesn’t sound like any of the crits I’ve ever done in my years of racing. What you described sounds more like a TT type effort.
Crits are very dynamic, there is a lot of variation in your power even when riding relatively efficiently simply due to all the corners plus the attacking style of racing that crits usually bring out in people.
Also, being a bigger rider (usually 165-170lbs) I’ve never managed to average anything close to 200w in any crit. The challenge lighter riders like yourself have is that you usually have to put out a similar number of watts to go the same speed which usually is a higher percentage of your FTP making it harder to sustain.
As for what you can do to race better in crits as a lightweight rider her is my list 1) learn to draft and race efficiently so you save energy until you have to use it. 2) Increase your short term power/repeatability to help you cope with the surges 3) increase your FTP to help you cope with the elevated pace of these short races. 4) race a lot and learn from your races, learn who the strong riders are in your races, learn how races usually play out (it’s different for teachnical courses, high speed non-tech course, and cross winds or rain will change the way a race plays out). 5) buy aero gear (wheels, skinsuit, helmet,etc…) This is speed you can instantly buy which reduces how hard you have to work. There is usually much more to be gained on the fitness side for most lower category riders, but those gains take months and years to develop. 6) race to your strengths, as a light rider you give less draft which can make it hard for people to draft off you effectively.
Strangely, that list mostly applies to all rider weights. You happen to be lighter than most folks, but the steps to racing better will be pretty similar to that of heavier riders.