FWIW, I thought I was fit going into my first race. I could outclimb most of my buddies and hang with the fastest guys in my club on club rides.

The constant slowing and surging out of every single corner took its toll on me quickly. I was shelled off the back in the first 25 minutes. Once off the back, it is just a matter of time before you get pulled or lapped; there is no prayer of a normal Joe bridging the gap to the field he couldn't hang with in the first place.

There is a LOT of value in losing, however.
For instance,
1: I have learned that you can't let a bunch of guys go past you one by one or all together and still expect to finish with the pack. That was a valuable lesson for me.
2: I have learned that I can redline my body at levels I had never seen before and I will live through the pain. That pain is an absolute wall if you have not encountered it frequently in the past. Only racing can give you that knowledge.
3: I have learned that sometimes being a better bike handler is more valueable than being a stronger rider. Every corner is a chance to gain a position or at least not blow your current position.
4: I have learned that those in the back of a field in a crit with a lot of corners have almost no chance of staying on: so it is worth whatever it costs to get up toward the front where you can avoid slowing so much in every corner.